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  19.   <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="前端" class="dropdown-title"><a href="/blog/web/" class="link-title">前端</a> <span class="title" style="display:none;">前端</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>前端文章</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/blog/pages/8143cc480faf9a11/" class="nav-link">JavaScript</a></li></ul></li><li class="dropdown-item"><h4>学习笔记</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/blog/note/javascript/" class="nav-link">《JavaScript教程》</a></li><li class="dropdown-subitem"><a href="/blog/note/js/" class="nav-link">《JavaScript高级程序设计》</a></li><li class="dropdown-subitem"><a href="/blog/note/es6/" class="nav-link">《ES6 教程》</a></li><li class="dropdown-subitem"><a href="/blog/note/vue/" class="nav-link">《Vue》</a></li><li class="dropdown-subitem"><a href="/blog/note/react/" class="nav-link">《React》</a></li><li class="dropdown-subitem"><a href="/blog/note/typescript-axios/" class="nav-link">《TypeScript 从零实现 axios》</a></li><li class="dropdown-subitem"><a href="/blog/note/git/" class="nav-link">《Git》</a></li><li class="dropdown-subitem"><a href="/blog/pages/51afd6/" class="nav-link">TypeScript</a></li><li class="dropdown-subitem"><a href="/blog/pages/4643cd/" class="nav-link">JS设计模式总结</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="页面" class="dropdown-title"><a href="/blog/ui/" class="link-title">页面</a> <span class="title" style="display:none;">页面</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/8309a5b876fc95e3/" class="nav-link">HTML</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/0a83b083bdf257cb/" class="nav-link">CSS</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="技术" class="dropdown-title"><a href="/blog/technology/" class="link-title">技术</a> <span class="title" style="display:none;">技术</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/9a7ee40fc232253e/" class="nav-link">技术文档</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/4c778760be26d8b3/" class="nav-link">GitHub技巧</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/117708e0af7f0bd9/" class="nav-link">Nodejs</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/41f87d890d0a02af/" class="nav-link">博客搭建</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="更多" class="dropdown-title"><a href="/blog/more/" class="link-title">更多</a> <span class="title" style="display:none;">更多</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/f2a556/" class="nav-link">学习</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/aea6571b7a8bae86/" class="nav-link">面试</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/2d615df9a36a98ed/" class="nav-link">心情杂货</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/baaa02/" class="nav-link">实用技巧</a></li><li class="dropdown-item"><!----> <a href="/blog/friends/" class="nav-link">友情链接</a></li></ul></div></div><div class="nav-item"><a href="/blog/about/" class="nav-link">关于</a></div><div class="nav-item"><a href="/blog/pages/beb6c0bd8a66cea6/" class="nav-link">收藏</a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="索引" class="dropdown-title"><a href="/blog/archives/" class="link-title">索引</a> <span class="title" style="display:none;">索引</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/categories/" class="nav-link">分类</a></li><li class="dropdown-item"><!----> <a href="/blog/tags/" class="nav-link">标签</a></li><li class="dropdown-item"><!----> <a href="/blog/archives/" class="nav-link">归档</a></li></ul></div></div> <a href="https://github.com/heBody/blog" target="_blank" rel="noopener noreferrer" class="repo-link">
    20. 

  20.     GitHub
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  21.     <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav></div></header> <div class="sidebar-mask"></div> <div class="sidebar-hover-trigger"></div> <aside class="sidebar" style="display:none;"><div class="blogger"><img src="https://fastly.jsdelivr.net/gh/xugaoyi/image_store/blog/20200103123203.jpg"> <div class="blogger-info"><h3>彪哥</h3> <span>爱好前端</span></div></div> <nav class="nav-links"><div class="nav-item"><a href="/blog/" class="nav-link">首页</a></div><div class="nav-item"><a href="http://fseller.com" target="_blank" rel="noopener noreferrer" class="nav-link external">
    22. 

  22.   个人游戏网站
    23. 

  23.   <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="前端" class="dropdown-title"><a href="/blog/web/" class="link-title">前端</a> <span class="title" style="display:none;">前端</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>前端文章</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/blog/pages/8143cc480faf9a11/" class="nav-link">JavaScript</a></li></ul></li><li class="dropdown-item"><h4>学习笔记</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/blog/note/javascript/" class="nav-link">《JavaScript教程》</a></li><li class="dropdown-subitem"><a href="/blog/note/js/" class="nav-link">《JavaScript高级程序设计》</a></li><li class="dropdown-subitem"><a href="/blog/note/es6/" class="nav-link">《ES6 教程》</a></li><li class="dropdown-subitem"><a href="/blog/note/vue/" class="nav-link">《Vue》</a></li><li class="dropdown-subitem"><a href="/blog/note/react/" class="nav-link">《React》</a></li><li class="dropdown-subitem"><a href="/blog/note/typescript-axios/" class="nav-link">《TypeScript 从零实现 axios》</a></li><li class="dropdown-subitem"><a href="/blog/note/git/" class="nav-link">《Git》</a></li><li class="dropdown-subitem"><a href="/blog/pages/51afd6/" class="nav-link">TypeScript</a></li><li class="dropdown-subitem"><a href="/blog/pages/4643cd/" class="nav-link">JS设计模式总结</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="页面" class="dropdown-title"><a href="/blog/ui/" class="link-title">页面</a> <span class="title" style="display:none;">页面</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/8309a5b876fc95e3/" class="nav-link">HTML</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/0a83b083bdf257cb/" class="nav-link">CSS</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="技术" class="dropdown-title"><a href="/blog/technology/" class="link-title">技术</a> <span class="title" style="display:none;">技术</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/9a7ee40fc232253e/" class="nav-link">技术文档</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/4c778760be26d8b3/" class="nav-link">GitHub技巧</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/117708e0af7f0bd9/" class="nav-link">Nodejs</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/41f87d890d0a02af/" class="nav-link">博客搭建</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="更多" class="dropdown-title"><a href="/blog/more/" class="link-title">更多</a> <span class="title" style="display:none;">更多</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/pages/f2a556/" class="nav-link">学习</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/aea6571b7a8bae86/" class="nav-link">面试</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/2d615df9a36a98ed/" class="nav-link">心情杂货</a></li><li class="dropdown-item"><!----> <a href="/blog/pages/baaa02/" class="nav-link">实用技巧</a></li><li class="dropdown-item"><!----> <a href="/blog/friends/" class="nav-link">友情链接</a></li></ul></div></div><div class="nav-item"><a href="/blog/about/" class="nav-link">关于</a></div><div class="nav-item"><a href="/blog/pages/beb6c0bd8a66cea6/" class="nav-link">收藏</a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="索引" class="dropdown-title"><a href="/blog/archives/" class="link-title">索引</a> <span class="title" style="display:none;">索引</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/blog/categories/" class="nav-link">分类</a></li><li class="dropdown-item"><!----> <a href="/blog/tags/" class="nav-link">标签</a></li><li class="dropdown-item"><!----> <a href="/blog/archives/" class="nav-link">归档</a></li></ul></div></div> <a href="https://github.com/heBody/blog" target="_blank" rel="noopener noreferrer" class="repo-link">
    24. 

  24.     GitHub
    25. 

  25.     <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav>  <ul class="sidebar-links"><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>基础</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>组件</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>过渡&amp;动画</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>可复用性&amp;组合</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>工具</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>规模化</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading open"><span>Vuex</span> <span class="arrow down"></span></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/blog/pages/b30620/" aria-current="page" class="active sidebar-link">Vuex</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level2"><a href="/blog/pages/b30620/#vuex使用过程演示" class="sidebar-link">Vuex使用过程演示</a></li><li class="sidebar-sub-header level2"><a href="/blog/pages/b30620/#核心概念" class="sidebar-link">核心概念</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/blog/pages/b30620/#state" class="sidebar-link">State</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#mapstate-辅助函数" class="sidebar-link">mapState 辅助函数</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#对象展开运算符" class="sidebar-link">对象展开运算符</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#组件仍然保有局部状态" class="sidebar-link">组件仍然保有局部状态</a></li><li class="sidebar-sub-header level3"><a href="/blog/pages/b30620/#getter" class="sidebar-link">Getter</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#通过属性访问" class="sidebar-link">通过属性访问</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#通过方法访问" class="sidebar-link">通过方法访问</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#mapgetters-辅助函数" class="sidebar-link">mapGetters 辅助函数</a></li><li class="sidebar-sub-header level3"><a href="/blog/pages/b30620/#mutation" class="sidebar-link">Mutation</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#提交载荷-payload" class="sidebar-link">提交载荷（Payload）</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#对象风格的提交方式" class="sidebar-link">对象风格的提交方式</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#mutation-需遵守-vue-的响应规则" class="sidebar-link">Mutation 需遵守 Vue 的响应规则</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#使用常量替代-mutation-事件类型" class="sidebar-link">使用常量替代 Mutation 事件类型</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#mutation-必须是同步函数" class="sidebar-link">Mutation 必须是同步函数</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#在组件中提交-mutation-mapmutations辅助函数" class="sidebar-link">在组件中提交 Mutation  (mapMutations辅助函数)</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#下一步-action" class="sidebar-link">下一步：Action</a></li><li class="sidebar-sub-header level3"><a href="/blog/pages/b30620/#action" class="sidebar-link">Action</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#分发-action" class="sidebar-link">分发 Action</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#在组件中分发-action-mapactions-辅助函数" class="sidebar-link">在组件中分发 Action  （mapActions 辅助函数）</a></li><li class="sidebar-sub-header level4"><a href="/blog/pages/b30620/#组合-action" class="sidebar-link">组合 Action</a></li></ul></li><li class="sidebar-sub-header level2"><a href="/blog/pages/b30620/#更多" class="sidebar-link">更多</a></li></ul></li></ul></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>其他</span> <span class="arrow right"></span></p> <!----></section></li></ul> </aside> <div><main class="page"><div class="theme-vdoing-wrapper "><div class="articleInfo-wrap" data-v-06225672><div class="articleInfo" data-v-06225672><ul class="breadcrumbs" data-v-06225672><li data-v-06225672><a href="/blog/" title="首页" class="iconfont icon-home router-link-active" data-v-06225672></a></li> <li data-v-06225672><a href="/blog/note/vue/#《Vue》笔记" data-v-06225672>《Vue》笔记</a></li><li data-v-06225672><a href="/blog/note/vue/#Vuex" data-v-06225672>Vuex</a></li></ul> <div class="info" data-v-06225672><div title="作者" class="author iconfont icon-touxiang" data-v-06225672><a href="https://github.com/heBody" target="_blank" title="作者" class="beLink" data-v-06225672>heBody</a></div> <div title="创建时间" class="date iconfont icon-riqi" data-v-06225672><a href="javascript:;" data-v-06225672>2020-08-08</a></div> <!----></div></div></div> <!----> <div class="content-wrapper"><div class="right-menu-wrapper"><div class="right-menu-margin"><div class="right-menu-title">目录</div> <div class="right-menu-content"></div></div></div> <h1><img src="data:image/png;base64,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">Vuex<!----></h1>  <div class="theme-vdoing-content content__default"><h1 id="vuex"><a href="#vuex" class="header-anchor">#</a> Vuex</h1> <p>Vuex 是一个专为 Vue.js 应用程序开发的<strong>状态管理模式</strong>。</p> <h2 id="vuex使用过程演示"><a href="#vuex使用过程演示" class="header-anchor">#</a> Vuex使用过程演示</h2> <p>以<code>vue-cli3</code>新创建出来的项目为例，演示Vuex的使用过程。</p> <p>创建项目:</p> <div class="language-sh line-numbers-mode"><pre class="language-sh"><code>vue create vuex-test
    26. 

  26. <span class="token builtin class-name">cd</span> vuex-test
    27. 

  27. <span class="token function">npm</span> run serve
    28. 

  28. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>安装<code>vuex</code>:</p> <div class="language-bash line-numbers-mode"><pre class="language-bash"><code><span class="token function">npm</span> i vuex <span class="token parameter variable">-S</span>
    29. 

  29. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><p>进入项目的<code>src/</code>下新建一个文件<code>store/index.js</code>，并写入：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token comment">// store/index.js</span>
    30. 

  30. <span class="token keyword">import</span> Vue <span class="token keyword">from</span> <span class="token string">'vue'</span>
    31. 

  31. <span class="token keyword">import</span> Vuex <span class="token keyword">from</span> <span class="token string">'vuex'</span>
    32. 

  32. 

  33. Vue<span class="token punctuation">.</span><span class="token function">use</span><span class="token punctuation">(</span>Vuex<span class="token punctuation">)</span>
    34. 

  34. 

  35. <span class="token keyword">const</span> store <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Vuex<span class="token punctuation">.</span>Store</span><span class="token punctuation">(</span><span class="token punctuation">{</span> <span class="token comment">// 容器 （构造函数Store开头大写）</span>
    36. 

  36.     <span class="token literal-property property">state</span><span class="token operator">:</span> <span class="token punctuation">{</span> <span class="token comment">// 状态</span>
    37. 

  37.         <span class="token literal-property property">count</span><span class="token operator">:</span> <span class="token number">0</span>
    38. 

  38.     <span class="token punctuation">}</span><span class="token punctuation">,</span>
    39. 

  39.     <span class="token literal-property property">mutations</span><span class="token operator">:</span> <span class="token punctuation">{</span> <span class="token comment">// 变化（使用mutations提交改变是为了方便追踪变化记录）</span>
    40. 

  40.         <span class="token function">increment</span> <span class="token punctuation">(</span><span class="token parameter">state</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    41. 

  41.             state<span class="token punctuation">.</span>count<span class="token operator">++</span>
    42. 

  42.         <span class="token punctuation">}</span>
    43. 

  43.     <span class="token punctuation">}</span>
    44. 

  44. <span class="token punctuation">}</span><span class="token punctuation">)</span>
    45. 

  45. <span class="token keyword">export</span> <span class="token keyword">default</span> store <span class="token comment">// 导出</span>
    46. 

  46. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br></div></div><p>进入<code>main.js</code> 注入<code>store</code>，<strong>使所有<code>vue</code>组件能够使用<code>vuex</code></strong> :</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token comment">// main.js</span>
    47. 

  47. <span class="token keyword">import</span> Vue <span class="token keyword">from</span> <span class="token string">'vue'</span>
    48. 

  48. <span class="token keyword">import</span> App <span class="token keyword">from</span> <span class="token string">'./App.vue'</span>
    49. 

  49. <span class="token keyword">import</span> router <span class="token keyword">from</span> <span class="token string">'./router'</span>
    50. 

  50. <span class="token keyword">import</span> store <span class="token keyword">from</span> <span class="token string">'./store'</span>
    51. 

  51. 

  52. Vue<span class="token punctuation">.</span>config<span class="token punctuation">.</span>productionTip <span class="token operator">=</span> <span class="token boolean">false</span>
    53. 

  53. 

  54. <span class="token keyword">new</span> <span class="token class-name">Vue</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    55. 

  55.   router<span class="token punctuation">,</span>
    56. 

  56.   store<span class="token punctuation">,</span>
    57. 

  57.   <span class="token function-variable function">render</span><span class="token operator">:</span> <span class="token parameter">h</span> <span class="token operator">=&gt;</span> <span class="token function">h</span><span class="token punctuation">(</span>App<span class="token punctuation">)</span>
    58. 

  58. <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">$mount</span><span class="token punctuation">(</span><span class="token string">'#app'</span><span class="token punctuation">)</span>
    59. 

  59. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br></div></div><p>现在我们可以从组件的方法提交一个变更：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">methods</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    60. 

  60.   <span class="token function">increment</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    61. 

  61.     <span class="token keyword">this</span><span class="token punctuation">.</span>$store<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'increment'</span><span class="token punctuation">)</span> <span class="token comment">// .commit('&lt;mutations里的事件名&gt;')</span>
    62. 

  62.     console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>$store<span class="token punctuation">.</span>state<span class="token punctuation">.</span>count<span class="token punctuation">)</span>
    63. 

  63.   <span class="token punctuation">}</span>
    64. 

  64. <span class="token punctuation">}</span>
    65. 

  65. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><p>在组件模板中使用状态：</p> <div class="language-vue line-numbers-mode"><pre class="language-vue"><code>{{ count }}
    66. 

  66. 

  67. computed: {
    68. 

  68. 	count() {
    69. 

  69. 		return this.$store.state.count
    70. 

  70. 	}
    71. 

  71. }
    72. 

  72. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><blockquote><p>state状态的改变会触发computed的重新计算</p></blockquote> <h2 id="核心概念"><a href="#核心概念" class="header-anchor">#</a> 核心概念</h2> <h3 id="state"><a href="#state" class="header-anchor">#</a> State</h3> <p>Vuex 使用<strong>单一状态树</strong>，每个应用将仅仅包含一个 store 实例</p> <h4 id="mapstate-辅助函数"><a href="#mapstate-辅助函数" class="header-anchor">#</a> <code>mapState</code> 辅助函数</h4> <p><strong>当一个组件需要获取多个状态的时候</strong>，将这些状态都声明为计算属性会有些重复和冗余。为了解决这个问题，我们可以使用 <code>mapState</code> 辅助函数帮助我们生成计算属性，让你少按几次键：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token comment">// 在单独构建的版本中辅助函数为 Vuex.mapState</span>
    73. 

  73. <span class="token keyword">import</span> <span class="token punctuation">{</span> mapState <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'vuex'</span>
    74. 

  74. 

  75. <span class="token keyword">export</span> <span class="token keyword">default</span> <span class="token punctuation">{</span>
    76. 

  76.   <span class="token comment">// ...</span>
    77. 

  77.   <span class="token literal-property property">computed</span><span class="token operator">:</span> <span class="token function">mapState</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    78. 

  78.     <span class="token comment">// 箭头函数可使代码更简练</span>
    79. 

  79.     <span class="token function-variable function">count</span><span class="token operator">:</span> <span class="token parameter">state</span> <span class="token operator">=&gt;</span> state<span class="token punctuation">.</span>count<span class="token punctuation">,</span>
    80. 

  80. 

  81.     <span class="token comment">// 传字符串参数 'count' 等同于 `state =&gt; state.count`</span>
    82. 

  82.     <span class="token literal-property property">countAlias</span><span class="token operator">:</span> <span class="token string">'count'</span><span class="token punctuation">,</span>
    83. 

  83. 

  84.     <span class="token comment">// 为了能够使用 `this` 获取局部状态，必须使用常规函数</span>
    85. 

  85.     <span class="token function">countPlusLocalState</span> <span class="token punctuation">(</span><span class="token parameter">state</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    86. 

  86.       <span class="token keyword">return</span> state<span class="token punctuation">.</span>count <span class="token operator">+</span> <span class="token keyword">this</span><span class="token punctuation">.</span>localCount
    87. 

  87.     <span class="token punctuation">}</span>
    88. 

  88.   <span class="token punctuation">}</span><span class="token punctuation">)</span>
    89. 

  89. <span class="token punctuation">}</span>
    90. 

  90. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br></div></div><p>上面mapState()参数内<strong>三个方式都是获取count的值</strong>。</p> <p>当映射的计算属性的名称与 state 的子节点名称相同时，我们也可以给 <code>mapState</code> 传一个字符串数组。</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">computed</span><span class="token operator">:</span> <span class="token function">mapState</span><span class="token punctuation">(</span><span class="token punctuation">[</span>
    91. 

  91.   <span class="token comment">// 映射 this.count 为 store.state.count</span>
    92. 

  92.   <span class="token string">'count'</span>
    93. 

  93. <span class="token punctuation">]</span><span class="token punctuation">)</span>
    94. 

  94. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><h4 id="对象展开运算符"><a href="#对象展开运算符" class="header-anchor">#</a> 对象展开运算符</h4> <p><code>mapState</code> 函数返回的是一个对象。可使用对象展开运算符将此对象混入到外部对象中</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">computed</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    95. 

  95.   <span class="token function">localComputed</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment">/* ... */</span> <span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token comment">// 其他的计算属性</span>
    96. 

  96.   <span class="token comment">// 使用对象展开运算符将此对象混入到外部对象中</span>
    97. 

  97.   <span class="token operator">...</span><span class="token function">mapState</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    98. 

  98.     <span class="token comment">// ... 这里面和上面的获取方式是一样的</span>
    99. 

  99.   <span class="token punctuation">}</span><span class="token punctuation">)</span>
    100. 

  100. <span class="token punctuation">}</span>
    101. 

  101. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><h4 id="组件仍然保有局部状态"><a href="#组件仍然保有局部状态" class="header-anchor">#</a> 组件仍然保有局部状态</h4> <p>使用 Vuex 并不意味着你需要将<strong>所有的</strong>状态放入 Vuex。虽然将所有的状态放到 Vuex 会使状态变化更显式和易调试，但也会使代码变得冗长和不直观。如果有些状态严格属于单个组件，最好还是作为组件的局部状态。你应该根据你的应用开发需要进行权衡和确定。</p> <h3 id="getter"><a href="#getter" class="header-anchor">#</a> Getter</h3> <p>有时候我们需要从 store 中的 state 中派生出一些状态，例如对列表进行过滤并计数：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">computed</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    102. 

  102.   <span class="token function">doneTodosCount</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    103. 

  103.     <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>$store<span class="token punctuation">.</span>state<span class="token punctuation">.</span>todos<span class="token punctuation">.</span><span class="token function">filter</span><span class="token punctuation">(</span><span class="token parameter">todo</span> <span class="token operator">=&gt;</span> todo<span class="token punctuation">.</span>done<span class="token punctuation">)</span><span class="token punctuation">.</span>length
    104. 

  104.   <span class="token punctuation">}</span>
    105. 

  105. <span class="token punctuation">}</span>
    106. 

  106. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><p>如果有多个组件需要用到此属性，我们要么复制这个函数，或者抽取到一个共享函数然后在多处导入它——无论哪种方式都不是很理想。</p> <p>Vuex 允许我们在 store 中定义“getter”（<strong>可以认为是 store 的计算属性</strong>）。就像计算属性一样，getter 的返回值会根据它的依赖<strong>被缓存</strong>起来，且只有当它的依赖值发生了改变才会被重新计算。</p> <p>Getter 接受 state 作为其第一个参数：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token keyword">const</span> store <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Vuex<span class="token punctuation">.</span>Store</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    107. 

  107.   <span class="token literal-property property">state</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    108. 

  108.     <span class="token literal-property property">todos</span><span class="token operator">:</span> <span class="token punctuation">[</span>
    109. 

  109.       <span class="token punctuation">{</span> <span class="token literal-property property">id</span><span class="token operator">:</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token literal-property property">text</span><span class="token operator">:</span> <span class="token string">'...'</span><span class="token punctuation">,</span> <span class="token literal-property property">done</span><span class="token operator">:</span> <span class="token boolean">true</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
    110. 

  110.       <span class="token punctuation">{</span> <span class="token literal-property property">id</span><span class="token operator">:</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token literal-property property">text</span><span class="token operator">:</span> <span class="token string">'...'</span><span class="token punctuation">,</span> <span class="token literal-property property">done</span><span class="token operator">:</span> <span class="token boolean">false</span> <span class="token punctuation">}</span>
    111. 

  111.     <span class="token punctuation">]</span>
    112. 

  112.   <span class="token punctuation">}</span><span class="token punctuation">,</span>
    113. 

  113.   <span class="token literal-property property">getters</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    114. 

  114.     <span class="token function-variable function">doneTodos</span><span class="token operator">:</span> <span class="token parameter">state</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    115. 

  115.       <span class="token keyword">return</span> state<span class="token punctuation">.</span>todos<span class="token punctuation">.</span><span class="token function">filter</span><span class="token punctuation">(</span><span class="token parameter">todo</span> <span class="token operator">=&gt;</span> todo<span class="token punctuation">.</span>done<span class="token punctuation">)</span>
    116. 

  116.     <span class="token punctuation">}</span>
    117. 

  117.   <span class="token punctuation">}</span>
    118. 

  118. <span class="token punctuation">}</span><span class="token punctuation">)</span>
    119. 

  119. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br></div></div><h4 id="通过属性访问"><a href="#通过属性访问" class="header-anchor">#</a> 通过属性访问</h4> <p>Getter 会暴露为 <code>store.getters</code> 对象，你可以以属性的形式访问这些值：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code>store<span class="token punctuation">.</span>getters<span class="token punctuation">.</span>doneTodos <span class="token comment">// -&gt; [{ id: 1, text: '...', done: true }]</span>
    120. 

  120. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><p>Getter 也可以接受其他 getter 作为第二个参数：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">getters</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    121. 

  121.   <span class="token comment">// ...</span>
    122. 

  122.   <span class="token function-variable function">doneTodosCount</span><span class="token operator">:</span> <span class="token punctuation">(</span><span class="token parameter">state<span class="token punctuation">,</span> getters</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    123. 

  123.     <span class="token keyword">return</span> getters<span class="token punctuation">.</span>doneTodos<span class="token punctuation">.</span>length
    124. 

  124.   <span class="token punctuation">}</span>
    125. 

  125. <span class="token punctuation">}</span>
    126. 

  126. store<span class="token punctuation">.</span>getters<span class="token punctuation">.</span>doneTodosCount <span class="token comment">// -&gt; 1</span>
    127. 

  127. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><p>我们可以很容易地在任何组件中使用它：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">computed</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    128. 

  128.   <span class="token function">doneTodosCount</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    129. 

  129.     <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>$store<span class="token punctuation">.</span>getters<span class="token punctuation">.</span>doneTodosCount
    130. 

  130.   <span class="token punctuation">}</span>
    131. 

  131. <span class="token punctuation">}</span>
    132. 

  132. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><p>注意，getter 在通过属性访问时是作为 Vue 的响应式系统的一部分缓存其中的。</p> <h4 id="通过方法访问"><a href="#通过方法访问" class="header-anchor">#</a> 通过方法访问</h4> <p>你也可以通过让 getter 返回一个函数，来<strong>实现给 getter 传参</strong>。在你对 store 里的数组进行查询时非常有用。</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">getters</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    133. 

  133.   <span class="token comment">// ...</span>
    134. 

  134.   <span class="token function-variable function">getTodoById</span><span class="token operator">:</span> <span class="token punctuation">(</span><span class="token parameter">state</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">(</span><span class="token parameter">id</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    135. 

  135.     <span class="token keyword">return</span> state<span class="token punctuation">.</span>todos<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token parameter">todo</span> <span class="token operator">=&gt;</span> todo<span class="token punctuation">.</span>id <span class="token operator">===</span> id<span class="token punctuation">)</span>
    136. 

  136.   <span class="token punctuation">}</span>
    137. 

  137. <span class="token punctuation">}</span>
    138. 

  138. store<span class="token punctuation">.</span>getters<span class="token punctuation">.</span><span class="token function">getTodoById</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span> <span class="token comment">// -&gt; { id: 2, text: '...', done: false }</span>
    139. 

  139. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><p>注意，getter 在通过方法访问时，每次都会去进行调用，而<strong>不会缓存结果</strong>。</p> <h4 id="mapgetters-辅助函数"><a href="#mapgetters-辅助函数" class="header-anchor">#</a> <code>mapGetters</code> 辅助函数</h4> <p><code>mapGetters</code> 辅助函数仅仅是将 store 中的 getter 映射到局部计算属性：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token keyword">import</span> <span class="token punctuation">{</span> mapGetters <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'vuex'</span>
    140. 

  140. 

  141. <span class="token keyword">export</span> <span class="token keyword">default</span> <span class="token punctuation">{</span>
    142. 

  142.   <span class="token comment">// ...</span>
    143. 

  143.   <span class="token literal-property property">computed</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    144. 

  144.   <span class="token comment">// 使用对象展开运算符将 getter 混入 computed 对象中</span>
    145. 

  145.     <span class="token operator">...</span><span class="token function">mapGetters</span><span class="token punctuation">(</span><span class="token punctuation">[</span>
    146. 

  146.       <span class="token string">'doneTodosCount'</span><span class="token punctuation">,</span>
    147. 

  147.       <span class="token string">'anotherGetter'</span><span class="token punctuation">,</span>
    148. 

  148.       <span class="token comment">// ...</span>
    149. 

  149.     <span class="token punctuation">]</span><span class="token punctuation">)</span>
    150. 

  150.   <span class="token punctuation">}</span>
    151. 

  151. <span class="token punctuation">}</span>
    152. 

  152. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br></div></div><p>如果你想将一个 getter 属性另取一个名字，使用对象形式：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token operator">...</span><span class="token function">mapGetters</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    153. 

  153.   <span class="token comment">// 把 `this.doneCount` 映射为 `this.$store.getters.doneTodosCount`</span>
    154. 

  154.   <span class="token literal-property property">doneCount</span><span class="token operator">:</span> <span class="token string">'doneTodosCount'</span>
    155. 

  155. <span class="token punctuation">}</span><span class="token punctuation">)</span>
    156. 

  156. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><h3 id="mutation"><a href="#mutation" class="header-anchor">#</a> Mutation</h3> <p>更改 Vuex 的 store 中的状态的<strong>唯一方法</strong>是提交 mutation。Vuex 中的 mutation 非常类似于事件：每个 mutation 都有一个字符串的 <strong>事件类型 (type)</strong> 和 一个 <strong>回调函数 (handler)</strong>。这个回调函数就是我们实际进行状态更改的地方，并且它会接受 state 作为第一个参数：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token keyword">const</span> store <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Vuex<span class="token punctuation">.</span>Store</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    157. 

  157.   <span class="token literal-property property">state</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    158. 

  158.     <span class="token literal-property property">count</span><span class="token operator">:</span> <span class="token number">1</span>
    159. 

  159.   <span class="token punctuation">}</span><span class="token punctuation">,</span>
    160. 

  160.   <span class="token literal-property property">mutations</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    161. 

  161.     <span class="token function">increment</span> <span class="token punctuation">(</span><span class="token parameter">state</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    162. 

  162.       <span class="token comment">// 变更状态</span>
    163. 

  163.       state<span class="token punctuation">.</span>count<span class="token operator">++</span>
    164. 

  164.     <span class="token punctuation">}</span>
    165. 

  165.   <span class="token punctuation">}</span>
    166. 

  166. <span class="token punctuation">}</span><span class="token punctuation">)</span>
    167. 

  167. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><p>你不能直接调用一个 mutation handler。这个选项更像是事件注册：“当触发一个类型为 <code>increment</code> 的 mutation 时，调用此函数。”要唤醒一个 mutation handler，你需要以相应的 type 调用 <strong>store.commit</strong> 方法：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code>store<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'increment'</span><span class="token punctuation">)</span>
    168. 

  168. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><h4 id="提交载荷-payload"><a href="#提交载荷-payload" class="header-anchor">#</a> 提交载荷（Payload）</h4> <p>你可以向 <code>store.commit</code> 传入额外的参数，即 mutation 的 <strong>载荷（payload）</strong>：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token comment">// ...</span>
    169. 

  169. <span class="token literal-property property">mutations</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    170. 

  170.   <span class="token function">increment</span> <span class="token punctuation">(</span><span class="token parameter">state<span class="token punctuation">,</span> n</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    171. 

  171.     state<span class="token punctuation">.</span>count <span class="token operator">+=</span> n
    172. 

  172.   <span class="token punctuation">}</span>
    173. 

  173. <span class="token punctuation">}</span>
    174. 

  174. store<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'increment'</span><span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">)</span>
    175. 

  175. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><p>在大多数情况下，载荷应该是一个对象，这样可以包含多个字段并且记录的 mutation 会更易读：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token comment">// ...</span>
    176. 

  176. <span class="token literal-property property">mutations</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    177. 

  177.   <span class="token function">increment</span> <span class="token punctuation">(</span><span class="token parameter">state<span class="token punctuation">,</span> payload</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    178. 

  178.     state<span class="token punctuation">.</span>count <span class="token operator">+=</span> payload<span class="token punctuation">.</span>amount
    179. 

  179.   <span class="token punctuation">}</span>
    180. 

  180. <span class="token punctuation">}</span>
    181. 

  181. store<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'increment'</span><span class="token punctuation">,</span> <span class="token punctuation">{</span>
    182. 

  182.   <span class="token literal-property property">amount</span><span class="token operator">:</span> <span class="token number">10</span>
    183. 

  183. <span class="token punctuation">}</span><span class="token punctuation">)</span>
    184. 

  184. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><h4 id="对象风格的提交方式"><a href="#对象风格的提交方式" class="header-anchor">#</a> 对象风格的提交方式</h4> <p>提交 mutation 的另一种方式是直接使用包含 <code>type</code> 属性的对象：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code>store<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    185. 

  185.   <span class="token literal-property property">type</span><span class="token operator">:</span> <span class="token string">'increment'</span><span class="token punctuation">,</span>
    186. 

  186.   <span class="token literal-property property">amount</span><span class="token operator">:</span> <span class="token number">10</span>
    187. 

  187. <span class="token punctuation">}</span><span class="token punctuation">)</span>
    188. 

  188. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><p>当使用对象风格的提交方式，整个对象都作为载荷传给 mutation 函数，因此 handler 保持不变：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">mutations</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    189. 

  189.   <span class="token function">increment</span> <span class="token punctuation">(</span><span class="token parameter">state<span class="token punctuation">,</span> payload</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    190. 

  190.     state<span class="token punctuation">.</span>count <span class="token operator">+=</span> payload<span class="token punctuation">.</span>amount
    191. 

  191.   <span class="token punctuation">}</span>
    192. 

  192. <span class="token punctuation">}</span>
    193. 

  193. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><h4 id="mutation-需遵守-vue-的响应规则"><a href="#mutation-需遵守-vue-的响应规则" class="header-anchor">#</a> Mutation 需遵守 Vue 的响应规则</h4> <p>既然 Vuex 的 store 中的状态是响应式的，那么当我们变更状态时，监视状态的 Vue 组件也会自动更新。这也意味着 Vuex 中的 mutation 也需要与使用 Vue 一样遵守一些注意事项：</p> <ol><li>最好提前在你的 store 中初始化好所有所需属性。</li> <li>当需要在对象上添加新属性时，你应该</li></ol> <ul><li><p>使用 <code>Vue.set(obj, 'newProp', 123)</code>, 或者</p></li> <li><p>以新对象替换老对象。例如，利用<a href="https://github.com/tc39/proposal-object-rest-spread" target="_blank" rel="noopener noreferrer">对象展开运算符<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a>我们可以这样写：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code>state<span class="token punctuation">.</span>obj <span class="token operator">=</span> <span class="token punctuation">{</span> <span class="token operator">...</span>state<span class="token punctuation">.</span>obj<span class="token punctuation">,</span> <span class="token literal-property property">newProp</span><span class="token operator">:</span> <span class="token number">123</span> <span class="token punctuation">}</span>
    194. 

  194. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div></li></ul> <h4 id="使用常量替代-mutation-事件类型"><a href="#使用常量替代-mutation-事件类型" class="header-anchor">#</a> 使用常量替代 Mutation 事件类型</h4> <p>使用常量替代 mutation 事件类型在各种 Flux 实现中是很常见的模式。这样可以使 linter 之类的工具发挥作用，同时把这些常量放在单独的文件中可以让你的代码合作者对整个 app 包含的 mutation 一目了然：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token comment">// mutation-types.js</span>
    195. 

  195. <span class="token keyword">export</span> <span class="token keyword">const</span> <span class="token constant">SOME_MUTATION</span> <span class="token operator">=</span> <span class="token string">'SOME_MUTATION'</span>
    196. 

  196. <span class="token comment">// store.js</span>
    197. 

  197. <span class="token keyword">import</span> Vuex <span class="token keyword">from</span> <span class="token string">'vuex'</span>
    198. 

  198. <span class="token keyword">import</span> <span class="token punctuation">{</span> <span class="token constant">SOME_MUTATION</span> <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'./mutation-types'</span>
    199. 

  199. 

  200. <span class="token keyword">const</span> store <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Vuex<span class="token punctuation">.</span>Store</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    201. 

  201.   <span class="token literal-property property">state</span><span class="token operator">:</span> <span class="token punctuation">{</span> <span class="token operator">...</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
    202. 

  202.   <span class="token literal-property property">mutations</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    203. 

  203.     <span class="token comment">// 我们可以使用 ES2015 风格的计算属性命名功能来使用一个常量作为函数名</span>
    204. 

  204.     <span class="token punctuation">[</span><span class="token constant">SOME_MUTATION</span><span class="token punctuation">]</span> <span class="token punctuation">(</span><span class="token parameter">state</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    205. 

  205.       <span class="token comment">// mutate state</span>
    206. 

  206.     <span class="token punctuation">}</span>
    207. 

  207.   <span class="token punctuation">}</span>
    208. 

  208. <span class="token punctuation">}</span><span class="token punctuation">)</span>
    209. 

  209. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br></div></div><p>用不用常量取决于你——在需要多人协作的大型项目中，这会很有帮助。但如果你不喜欢，你完全可以不这样做。</p> <h4 id="mutation-必须是同步函数"><a href="#mutation-必须是同步函数" class="header-anchor">#</a> Mutation 必须是同步函数</h4> <p>一条重要的原则就是要记住 <strong>mutation 必须是同步函数</strong>。为什么？请参考下面的例子：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">mutations</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    210. 

  210.   <span class="token function">someMutation</span> <span class="token punctuation">(</span><span class="token parameter">state</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    211. 

  211.     api<span class="token punctuation">.</span><span class="token function">callAsyncMethod</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    212. 

  212.       state<span class="token punctuation">.</span>count<span class="token operator">++</span>
    213. 

  213.     <span class="token punctuation">}</span><span class="token punctuation">)</span>
    214. 

  214.   <span class="token punctuation">}</span>
    215. 

  215. <span class="token punctuation">}</span>
    216. 

  216. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><p>现在想象，我们正在 debug 一个 app 并且观察 devtool 中的 mutation 日志。每一条 mutation 被记录，devtools 都需要捕捉到前一状态和后一状态的快照。然而，在上面的例子中 mutation 中的异步函数中的回调让这不可能完成：因为当 mutation 触发的时候，回调函数还没有被调用，devtools 不知道什么时候回调函数实际上被调用——实质上任何在回调函数中进行的状态的改变都是不可追踪的。</p> <h4 id="在组件中提交-mutation-mapmutations辅助函数"><a href="#在组件中提交-mutation-mapmutations辅助函数" class="header-anchor">#</a> 在组件中提交 Mutation  (<code>mapMutations</code>辅助函数)</h4> <p>你可以在组件中使用 <code>this.$store.commit('xxx')</code> 提交 mutation，或者使用 <code>mapMutations</code> 辅助函数将组件中的 methods 映射为 <code>store.commit</code> 调用（需要在根节点注入 <code>store</code>）。</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token keyword">import</span> <span class="token punctuation">{</span> mapMutations <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'vuex'</span>
    217. 

  217. 

  218. <span class="token keyword">export</span> <span class="token keyword">default</span> <span class="token punctuation">{</span>
    219. 

  219.   <span class="token comment">// ...</span>
    220. 

  220.   <span class="token literal-property property">methods</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    221. 

  221.     <span class="token operator">...</span><span class="token function">mapMutations</span><span class="token punctuation">(</span><span class="token punctuation">[</span>
    222. 

  222.       <span class="token string">'increment'</span><span class="token punctuation">,</span> <span class="token comment">// 将 `this.increment()` 映射为 `this.$store.commit('increment')`</span>
    223. 

  223. 

  224.       <span class="token comment">// `mapMutations` 也支持载荷：</span>
    225. 

  225.       <span class="token string">'incrementBy'</span> <span class="token comment">// 将 `this.incrementBy(amount)` 映射为 `this.$store.commit('incrementBy', amount)`</span>
    226. 

  226.     <span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
    227. 

  227.     <span class="token operator">...</span><span class="token function">mapMutations</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    228. 

  228.       <span class="token literal-property property">add</span><span class="token operator">:</span> <span class="token string">'increment'</span> <span class="token comment">// 将 `this.add()` 映射为 `this.$store.commit('increment')`</span>
    229. 

  229.     <span class="token punctuation">}</span><span class="token punctuation">)</span>
    230. 

  230.   <span class="token punctuation">}</span>
    231. 

  231. <span class="token punctuation">}</span>
    232. 

  232. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br></div></div><h4 id="下一步-action"><a href="#下一步-action" class="header-anchor">#</a> 下一步：Action</h4> <p>在 mutation 中混合异步调用会导致你的程序很难调试。例如，当你调用了两个包含异步回调的 mutation 来改变状态，你怎么知道什么时候回调和哪个先回调呢？这就是为什么我们要区分这两个概念。在 Vuex 中，<strong>mutation 都是同步事务</strong>：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code>store<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'increment'</span><span class="token punctuation">)</span>
    233. 

  233. <span class="token comment">// 任何由 &quot;increment&quot; 导致的状态变更都应该在此刻完成。</span>
    234. 

  234. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><p>为了处理异步操作，让我们来看一看 <a href="https://vuex.vuejs.org/zh/guide/actions.html" target="_blank" rel="noopener noreferrer">Action<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a>。</p> <h3 id="action"><a href="#action" class="header-anchor">#</a> Action</h3> <p>Action 类似于 mutation，不同在于：</p> <ul><li>Action 提交的是 mutation，而不是直接变更状态。</li> <li>Action 可以包含任意异步操作。</li></ul> <p>让我们来注册一个简单的 action：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token keyword">const</span> store <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Vuex<span class="token punctuation">.</span>Store</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    235. 

  235.   <span class="token literal-property property">state</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    236. 

  236.     <span class="token literal-property property">count</span><span class="token operator">:</span> <span class="token number">0</span>
    237. 

  237.   <span class="token punctuation">}</span><span class="token punctuation">,</span>
    238. 

  238.   <span class="token literal-property property">mutations</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    239. 

  239.     <span class="token function">increment</span> <span class="token punctuation">(</span><span class="token parameter">state</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    240. 

  240.       state<span class="token punctuation">.</span>count<span class="token operator">++</span>
    241. 

  241.     <span class="token punctuation">}</span>
    242. 

  242.   <span class="token punctuation">}</span><span class="token punctuation">,</span>
    243. 

  243.   <span class="token literal-property property">actions</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    244. 

  244.     <span class="token function">increment</span> <span class="token punctuation">(</span><span class="token parameter">context</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    245. 

  245.       context<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'increment'</span><span class="token punctuation">)</span>
    246. 

  246.     <span class="token punctuation">}</span>
    247. 

  247.   <span class="token punctuation">}</span>
    248. 

  248. <span class="token punctuation">}</span><span class="token punctuation">)</span>
    249. 

  249. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br></div></div><p><strong>Action 函数接受一个与 store 实例具有相同方法和属性的 context 对象</strong>，因此你可以调用 <code>context.commit</code> 提交一个 mutation，或者通过 <code>context.state</code> 和 <code>context.getters</code> 来获取 state 和 getters。当我们在之后介绍到 <a href="https://vuex.vuejs.org/zh/guide/modules.html" target="_blank" rel="noopener noreferrer">Modules<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a> 时，你就知道 context 对象为什么不是 store 实例本身了。</p> <p>实践中，我们会经常用到 ES2015 的 <a href="https://github.com/lukehoban/es6features#destructuring" target="_blank" rel="noopener noreferrer">参数解构<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a> 来简化代码（特别是我们需要调用 <code>commit</code> 很多次的时候）：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">actions</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    250. 

  250.   <span class="token function">increment</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token punctuation">{</span> commit <span class="token punctuation">}</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    251. 

  251.     <span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'increment'</span><span class="token punctuation">)</span>
    252. 

  252.   <span class="token punctuation">}</span>
    253. 

  253. <span class="token punctuation">}</span>
    254. 

  254. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><h4 id="分发-action"><a href="#分发-action" class="header-anchor">#</a> 分发 Action</h4> <p><strong>Action 通过 <code>store.dispatch</code> 方法触发</strong>：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code>store<span class="token punctuation">.</span><span class="token function">dispatch</span><span class="token punctuation">(</span><span class="token string">'increment'</span><span class="token punctuation">)</span>
    255. 

  255. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><p>乍一眼看上去感觉多此一举，我们直接分发 mutation 岂不更方便？实际上并非如此，还记得 <strong>mutation 必须同步执行</strong>这个限制么？Action 就不受约束！我们可以在 action 内部执行<strong>异步</strong>操作：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">actions</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    256. 

  256.   <span class="token function">incrementAsync</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token punctuation">{</span> commit <span class="token punctuation">}</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    257. 

  257.     <span class="token function">setTimeout</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    258. 

  258.       <span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'increment'</span><span class="token punctuation">)</span>
    259. 

  259.     <span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token number">1000</span><span class="token punctuation">)</span>
    260. 

  260.   <span class="token punctuation">}</span>
    261. 

  261. <span class="token punctuation">}</span>
    262. 

  262. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><p>Actions 支持同样的载荷方式和对象方式进行分发：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token comment">// 以载荷形式分发</span>
    263. 

  263. store<span class="token punctuation">.</span><span class="token function">dispatch</span><span class="token punctuation">(</span><span class="token string">'incrementAsync'</span><span class="token punctuation">,</span> <span class="token punctuation">{</span>
    264. 

  264.   <span class="token literal-property property">amount</span><span class="token operator">:</span> <span class="token number">10</span>
    265. 

  265. <span class="token punctuation">}</span><span class="token punctuation">)</span>
    266. 

  266. 

  267. <span class="token comment">// 以对象形式分发</span>
    268. 

  268. store<span class="token punctuation">.</span><span class="token function">dispatch</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    269. 

  269.   <span class="token literal-property property">type</span><span class="token operator">:</span> <span class="token string">'incrementAsync'</span><span class="token punctuation">,</span>
    270. 

  270.   <span class="token literal-property property">amount</span><span class="token operator">:</span> <span class="token number">10</span>
    271. 

  271. <span class="token punctuation">}</span><span class="token punctuation">)</span>
    272. 

  272. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><p>来看一个更加实际的购物车示例，涉及到<strong>调用异步 API</strong> 和<strong>分发多重 mutation</strong>：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">actions</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    273. 

  273.   <span class="token function">checkout</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token punctuation">{</span> commit<span class="token punctuation">,</span> state <span class="token punctuation">}</span><span class="token punctuation">,</span> products</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    274. 

  274.     <span class="token comment">// 把当前购物车的物品备份起来</span>
    275. 

  275.     <span class="token keyword">const</span> savedCartItems <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token operator">...</span>state<span class="token punctuation">.</span>cart<span class="token punctuation">.</span>added<span class="token punctuation">]</span>
    276. 

  276.     <span class="token comment">// 发出结账请求，然后乐观地清空购物车</span>
    277. 

  277.     <span class="token function">commit</span><span class="token punctuation">(</span>types<span class="token punctuation">.</span><span class="token constant">CHECKOUT_REQUEST</span><span class="token punctuation">)</span>
    278. 

  278.     <span class="token comment">// 购物 API 接受一个成功回调和一个失败回调</span>
    279. 

  279.     shop<span class="token punctuation">.</span><span class="token function">buyProducts</span><span class="token punctuation">(</span>
    280. 

  280.       products<span class="token punctuation">,</span>
    281. 

  281.       <span class="token comment">// 成功操作</span>
    282. 

  282.       <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token function">commit</span><span class="token punctuation">(</span>types<span class="token punctuation">.</span><span class="token constant">CHECKOUT_SUCCESS</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
    283. 

  283.       <span class="token comment">// 失败操作</span>
    284. 

  284.       <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token function">commit</span><span class="token punctuation">(</span>types<span class="token punctuation">.</span><span class="token constant">CHECKOUT_FAILURE</span><span class="token punctuation">,</span> savedCartItems<span class="token punctuation">)</span>
    285. 

  285.     <span class="token punctuation">)</span>
    286. 

  286.   <span class="token punctuation">}</span>
    287. 

  287. <span class="token punctuation">}</span>
    288. 

  288. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br></div></div><p>注意我们正在进行一系列的异步操作，并且通过提交 mutation 来记录 action 产生的副作用（即状态变更）。</p> <h4 id="在组件中分发-action-mapactions-辅助函数"><a href="#在组件中分发-action-mapactions-辅助函数" class="header-anchor">#</a> 在组件中分发 Action  （<code>mapActions</code> 辅助函数）</h4> <p>你在组件中使用 <code>this.$store.dispatch('xxx')</code> 分发 action，或者使用 <code>mapActions</code> 辅助函数将组件的 methods 映射为 <code>store.dispatch</code> 调用（需要先在根节点注入 <code>store</code>）：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token keyword">import</span> <span class="token punctuation">{</span> mapActions <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'vuex'</span>
    289. 

  289. 

  290. <span class="token keyword">export</span> <span class="token keyword">default</span> <span class="token punctuation">{</span>
    291. 

  291.   <span class="token comment">// ...</span>
    292. 

  292.   <span class="token literal-property property">methods</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    293. 

  293.     <span class="token operator">...</span><span class="token function">mapActions</span><span class="token punctuation">(</span><span class="token punctuation">[</span>
    294. 

  294.       <span class="token string">'increment'</span><span class="token punctuation">,</span> <span class="token comment">// 将 `this.increment()` 映射为 `this.$store.dispatch('increment')`</span>
    295. 

  295. 

  296.       <span class="token comment">// `mapActions` 也支持载荷：</span>
    297. 

  297.       <span class="token string">'incrementBy'</span> <span class="token comment">// 将 `this.incrementBy(amount)` 映射为 `this.$store.dispatch('incrementBy', amount)`</span>
    298. 

  298.     <span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
    299. 

  299.     <span class="token operator">...</span><span class="token function">mapActions</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    300. 

  300.       <span class="token literal-property property">add</span><span class="token operator">:</span> <span class="token string">'increment'</span> <span class="token comment">// 将 `this.add()` 映射为 `this.$store.dispatch('increment')`</span>
    301. 

  301.     <span class="token punctuation">}</span><span class="token punctuation">)</span>
    302. 

  302.   <span class="token punctuation">}</span>
    303. 

  303. <span class="token punctuation">}</span>
    304. 

  304. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br></div></div><h4 id="组合-action"><a href="#组合-action" class="header-anchor">#</a> 组合 Action</h4> <p>Action 通常是异步的，那么如何知道 action 什么时候结束呢？更重要的是，我们如何才能组合多个 action，以处理更加复杂的异步流程？</p> <p>首先，你需要明白 <code>store.dispatch</code> 可以处理被触发的 action 的处理函数返回的 Promise，并且 <code>store.dispatch</code> 仍旧返回 Promise：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">actions</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    305. 

  305.   <span class="token function">actionA</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token punctuation">{</span> commit <span class="token punctuation">}</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    306. 

  306.     <span class="token keyword">return</span> <span class="token keyword">new</span> <span class="token class-name">Promise</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">resolve<span class="token punctuation">,</span> reject</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    307. 

  307.       <span class="token function">setTimeout</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    308. 

  308.         <span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'someMutation'</span><span class="token punctuation">)</span>
    309. 

  309.         <span class="token function">resolve</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
    310. 

  310.       <span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token number">1000</span><span class="token punctuation">)</span>
    311. 

  311.     <span class="token punctuation">}</span><span class="token punctuation">)</span>
    312. 

  312.   <span class="token punctuation">}</span>
    313. 

  313. <span class="token punctuation">}</span>
    314. 

  314. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><p>现在你可以：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code>store<span class="token punctuation">.</span><span class="token function">dispatch</span><span class="token punctuation">(</span><span class="token string">'actionA'</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">then</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    315. 

  315.   <span class="token comment">// ...</span>
    316. 

  316. <span class="token punctuation">}</span><span class="token punctuation">)</span>
    317. 

  317. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>在另外一个 action 中也可以：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token literal-property property">actions</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    318. 

  318.   <span class="token comment">// ...</span>
    319. 

  319.   <span class="token function">actionB</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token punctuation">{</span> dispatch<span class="token punctuation">,</span> commit <span class="token punctuation">}</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    320. 

  320.     <span class="token keyword">return</span> <span class="token function">dispatch</span><span class="token punctuation">(</span><span class="token string">'actionA'</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">then</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    321. 

  321.       <span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'someOtherMutation'</span><span class="token punctuation">)</span>
    322. 

  322.     <span class="token punctuation">}</span><span class="token punctuation">)</span>
    323. 

  323.   <span class="token punctuation">}</span>
    324. 

  324. <span class="token punctuation">}</span>
    325. 

  325. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><p>最后，如果我们利用 <a href="https://tc39.github.io/ecmascript-asyncawait/" target="_blank" rel="noopener noreferrer">async / await<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a>，我们可以如下组合 action：</p> <div class="language-js line-numbers-mode"><pre class="language-js"><code><span class="token comment">// 假设 getData() 和 getOtherData() 返回的是 Promise</span>
    326. 

  326. 

  327. <span class="token literal-property property">actions</span><span class="token operator">:</span> <span class="token punctuation">{</span>
    328. 

  328.   <span class="token keyword">async</span> <span class="token function">actionA</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token punctuation">{</span> commit <span class="token punctuation">}</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    329. 

  329.     <span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'gotData'</span><span class="token punctuation">,</span> <span class="token keyword">await</span> <span class="token function">getData</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
    330. 

  330.   <span class="token punctuation">}</span><span class="token punctuation">,</span>
    331. 

  331.   <span class="token keyword">async</span> <span class="token function">actionB</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token punctuation">{</span> dispatch<span class="token punctuation">,</span> commit <span class="token punctuation">}</span></span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    332. 

  332.     <span class="token keyword">await</span> <span class="token function">dispatch</span><span class="token punctuation">(</span><span class="token string">'actionA'</span><span class="token punctuation">)</span> <span class="token comment">// 等待 actionA 完成</span>
    333. 

  333.     <span class="token function">commit</span><span class="token punctuation">(</span><span class="token string">'gotOtherData'</span><span class="token punctuation">,</span> <span class="token keyword">await</span> <span class="token function">getOtherData</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
    334. 

  334.   <span class="token punctuation">}</span>
    335. 

  335. <span class="token punctuation">}</span>
    336. 

  336. </code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><blockquote><p>一个 <code>store.dispatch</code> 在不同模块中可以触发多个 action 函数。在这种情况下，只有当所有触发函数完成后，返回的 Promise 才会执行。</p></blockquote> <h2 id="更多"><a href="#更多" class="header-anchor">#</a> 更多</h2> <p>更多内容查看官方文档：<a href="https://vuex.vuejs.org/zh/guide/modules.html" target="_blank" rel="noopener noreferrer">https://vuex.vuejs.org/zh/guide/modules.html<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></p></div></div>  <div class="page-edit"><div class="edit-link"><a href="https://github.com/heBody/blog/edit/master/docs/《Vue》笔记/10.Vuex/01.Vuex.md" target="_blank" rel="noopener noreferrer">编辑</a> <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></div> <!----> <div class="last-updated"><span class="prefix">上次更新:</span> <span class="time">2022/12/14, 19:36:42</span></div></div> <div class="page-nav-wapper"><div class="page-nav-centre-wrap"><a href="/blog/pages/38ecac9a9b92f037/" class="page-nav-centre page-nav-centre-prev"><div class="tooltip">路由懒加载</div></a> <a href="/blog/pages/fb08e252dfd8fdfd/" class="page-nav-centre page-nav-centre-next"><div class="tooltip">Vue中的防抖函数封装和使用</div></a></div> <div class="page-nav"><p class="inner"><span class="prev">
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