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class="sidebar-link">State&amp;生命周期</a></li><li><a href="/blog/pages/f27775/" class="sidebar-link">事件处理</a></li><li><a href="/blog/pages/8fcda8/" class="sidebar-link">条件渲染</a></li><li><a href="/blog/pages/88f4b0/" class="sidebar-link">列表&amp;Key</a></li><li><a href="/blog/pages/002db7/" class="sidebar-link">表单</a></li><li><a href="/blog/pages/f0e3d2/" aria-current="page" class="active sidebar-link">状态提升 (共享状态)</a><ul class="sidebar-sub-headers"></ul></li><li><a href="/blog/pages/9ae8e8/" class="sidebar-link">组合vs继承</a></li><li><a href="/blog/pages/c689bf/" class="sidebar-link">React哲学</a></li></ul></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>高级指引</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Hook</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>案例演示</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-06970110><div class="articleInfo" data-v-06970110><ul class="breadcrumbs" data-v-06970110><li data-v-06970110><a href="/blog/" title="首页" class="iconfont icon-home router-link-active" data-v-06970110></a></li> <li data-v-06970110><a href="/blog/note/react/#《React》笔记" data-v-06970110>《React》笔记</a></li><li data-v-06970110><a href="/blog/note/react/#核心概念" data-v-06970110>核心概念</a></li></ul> <div class="info" data-v-06970110><div title="作者" class="author iconfont icon-touxiang" data-v-06970110><a href="https://github.com/heBody" target="_blank" title="作者" class="beLink" data-v-06970110>heBody</a></div> <div title="创建时间" class="date iconfont icon-riqi" data-v-06970110><a href="javascript:;" data-v-06970110>2021-03-26</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,iVBORw0KGgoAAAANSUhEUgAAAB4AAAAeCAYAAAA7MK6iAAAAAXNSR0IArs4c6QAABH1JREFUSA3tVl1oHFUUPmdmd2ltklqbpJDiNnXFmgbFktho7YMPNiJSSZM0+CAYSkUELVhM6YuwIPpgoOKDqOBDC0XE2CQoNtQXBUFTTcCi+Wlh1V2TQExsUzcltd3M9Tt3ZjZzZ2fT+OJTL8yeM+eee757fmeJbq//KQL8X3DUSFOcfr7cRsRtxNQMWueeVzOkaITIGqQHNg5y8+jNW9ldM7A6nTpAjuolUikAwq7CE3WcM2RRDz+XGVgN3FptU/aUSlvq9Pa3iZ1+sgAqJyyAFqkipd9dqiwHF3P65YycLWc/6sqGrvoEoIp6DOFaX5h6+dnfjkWprwqsPk0dUGq5vySwDImC10KxFHgGL1SWoc92O3eVht09qdXNH11I2SsTsJYqMWzihqGMi+A+Garf3BAuuLI5oGlULyNfyB/HYNujwktOfRrMr5t77NmevqaUopx0grnKAyvVpmwUDB4x6FPXuGvYLTDwWsejwgtgkYKPqRJg8SV6xaiZ3ZTppGneS4yfH5/66fZSDHv+QZci/+h5c5UHtpy67JUqGppM0sh0Nc1dW6/N1W5Yoqat8/TU/VnadmdeW2PLLSyh0cvxBs3KbqTmwYPpxN4do/mzE8nEpvX/UMu2Wbp74zUAK5q6WkHns7V0eWkdPbPzd3rxkTGybadYySumVzhcaJFbs5UrEkQ/+CK8gF5dnh/6ciIZ73gwQ927L1IitoxKLXYP3SjYdOrHHfTZhRRlFyrorafPk20B3HPD1y2G3qKZME5Jcf3t/HUC13/8tSd++vqFveMUTwAUxSUFI1QekR1+bIze3D9MF2aq6cPvG72CgnldWCFqyRw3lwH8ZMerjTD9ElRO7Gv44wNpC90aASqGfVlz/Rx17srQ57/UU26hkhQqUB7dBR71WmzQhHUnblGmVOEw0jhbV1n9OlXUDCIRGaNV5Jp43N516fN7JmnTHdfp7Hgy0luO4aMhtkLL8Bi3bUWYvzh5Mn1dTxrL6QmGuRhGL/TiTTxRoEdTszSaq9GR0NGA3KdkOz3hqSV3MIDhQ5IVX/Ivx3umBti2es2h4eZby7x8br1rkf7Mo90AqC8aQ3sJeNzqFRu+vSANAQe3PL7l0HGOAdwDCeZYvNKeoZp1Qfs6Aipndh86HmFRi0LAnEO47wsqM6cdfjh3jBPUzhZy7nvlUfFsamED1VQt6aISHVymXZ/B2aCtIG8AI8xfobj2d3en1wWVhOeHELKmLQ1s211s88comkv4UCwWyF787mJdYXtNfhKAXVqnKTq8QZvGAGGOfaTo5pGZ/PwbUCr5+DPr/1J92JNHr9aOl/F3iI5+O1nfybsGxoimvZ3ViWSluDITw3P37mypheDIPY0tw7+O/5ApbkYw+zpfaUVu32Pi98+defdUhEpZkRFq0aqyNh9FuL9hpYbEm6iwi0z2REd09ZmyENEbuhjDWzKvZXTqKYaBIr3tt5kuPtQBZFvEUwHt60vfCNu41XsksH9Ij1BMMz1Y0OOunHNShFIP5868g5zeXmuLwL9T4b6Q2+KejgAAAABJRU5ErkJggg==">状态提升 (共享状态)<!----></h1>  <div class="theme-vdoing-content content__default"><h1 id="_09-状态提升-共享状态"><a href="#_09-状态提升-共享状态" class="header-anchor">#</a> 09. 状态提升 (共享状态)</h1> <p>通常，<strong>多个组件需要反映相同的变化数据，这时我们建议将共享状态提升到最近的共同父组件中去</strong>。</p> <p>在 React 中，<strong>将多个组件中需要共享的 state 向上移动到它们的最近共同父组件中，便可实现共享 state。这就是所谓的“状态提升”</strong></p> <p>两个输入框共享数据的例子：</p> <div class="language-jsx line-numbers-mode"><pre class="language-jsx"><code><span class="token keyword">const</span> scaleNames <span class="token operator">=</span> <span class="token punctuation">{</span>
  <span class="token literal-property property">c</span><span class="token operator">:</span> <span class="token string">'摄氏度'</span><span class="token punctuation">,</span>
  <span class="token literal-property property">f</span><span class="token operator">:</span> <span class="token string">'华氏度'</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>

<span class="token comment">// 转摄氏度</span>
<span class="token keyword">function</span> <span class="token function">toCelsius</span><span class="token punctuation">(</span><span class="token parameter">fahrenheit</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token keyword">return</span> <span class="token punctuation">(</span>fahrenheit <span class="token operator">-</span> <span class="token number">32</span><span class="token punctuation">)</span> <span class="token operator">*</span> <span class="token number">5</span> <span class="token operator">/</span> <span class="token number">9</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">// 转华氏度</span>
<span class="token keyword">function</span> <span class="token function">toFahrenheit</span><span class="token punctuation">(</span><span class="token parameter">celsius</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token keyword">return</span> <span class="token punctuation">(</span>celsius <span class="token operator">*</span> <span class="token number">9</span> <span class="token operator">/</span> <span class="token number">5</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">32</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">// 转换，为空时返回空，否则返回保留三位小数的浮点数</span>
<span class="token keyword">function</span> <span class="token function">tryConvert</span><span class="token punctuation">(</span><span class="token parameter">temperature<span class="token punctuation">,</span> convert</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token keyword">const</span> input <span class="token operator">=</span> <span class="token function">parseFloat</span><span class="token punctuation">(</span>temperature<span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token keyword">if</span> <span class="token punctuation">(</span>Number<span class="token punctuation">.</span><span class="token function">isNaN</span><span class="token punctuation">(</span>input<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> <span class="token string">''</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
  <span class="token keyword">const</span> output <span class="token operator">=</span> <span class="token function">convert</span><span class="token punctuation">(</span>input<span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token comment">// Math.round返回一个数字四舍五入后的整数</span>
  <span class="token keyword">const</span> rounded <span class="token operator">=</span> Math<span class="token punctuation">.</span><span class="token function">round</span><span class="token punctuation">(</span>output <span class="token operator">*</span> <span class="token number">1000</span><span class="token punctuation">)</span> <span class="token operator">/</span> <span class="token number">1000</span><span class="token punctuation">;</span>
  <span class="token keyword">return</span> rounded<span class="token punctuation">.</span><span class="token function">toString</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">// 水是否会沸腾</span>
<span class="token keyword">function</span> <span class="token function">BoilingVerdict</span><span class="token punctuation">(</span><span class="token parameter">props</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token keyword">if</span> <span class="token punctuation">(</span>props<span class="token punctuation">.</span>celsius <span class="token operator">&gt;=</span> <span class="token number">100</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>p</span><span class="token punctuation">&gt;</span></span><span class="token plain-text">水会沸腾.</span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>p</span><span class="token punctuation">&gt;</span></span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
  <span class="token keyword">return</span> <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>p</span><span class="token punctuation">&gt;</span></span><span class="token plain-text">水不会沸腾.</span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>p</span><span class="token punctuation">&gt;</span></span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">// 子组件 - 输入框</span>
<span class="token keyword">class</span> <span class="token class-name">TemperatureInput</span> <span class="token keyword">extends</span> <span class="token class-name">React<span class="token punctuation">.</span>Component</span> <span class="token punctuation">{</span>
  <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">props</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">super</span><span class="token punctuation">(</span>props<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 接收父组件传入props</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span>handleChange <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">handleChange</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 绑定回调函数，并修正this</span>
  <span class="token punctuation">}</span>
	
  <span class="token comment">// 处理change</span>
  <span class="token function">handleChange</span><span class="token punctuation">(</span><span class="token parameter">e</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// e是合成事件对象，通过e.target.value 取值</span>
    <span class="token comment">// 调用父组件传入的onTemperatureChange函数，并传值</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span>props<span class="token punctuation">.</span><span class="token function">onTemperatureChange</span><span class="token punctuation">(</span>e<span class="token punctuation">.</span>target<span class="token punctuation">.</span>value<span class="token punctuation">)</span><span class="token punctuation">;</span>
    
    <span class="token comment">// 当子组件输入框值改变时调用父组件的onTemperatureChange方法，并传出值。</span>
    <span class="token comment">// 另外，onTemperatureChange命名方式：`在&lt;子组件&gt;变更`</span>
  <span class="token punctuation">}</span>

  <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// 接收父组件传入的温度值</span>
    <span class="token keyword">const</span> temperature <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>props<span class="token punctuation">.</span>temperature<span class="token punctuation">;</span>
    <span class="token comment">// 接收父组件传入的衡量方式</span>
    <span class="token keyword">const</span> scale <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>props<span class="token punctuation">.</span>scale<span class="token punctuation">;</span>
    
    <span class="token keyword">return</span> <span class="token punctuation">(</span>
      <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>fieldset</span><span class="token punctuation">&gt;</span></span><span class="token plain-text">
        </span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>legend</span><span class="token punctuation">&gt;</span></span><span class="token plain-text">输入温度-</span><span class="token punctuation">{</span>scaleNames<span class="token punctuation">[</span>scale<span class="token punctuation">]</span><span class="token punctuation">}</span><span class="token plain-text">:</span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>legend</span><span class="token punctuation">&gt;</span></span><span class="token plain-text">
        </span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>input</span> <span class="token attr-name">value</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span>temperature<span class="token punctuation">}</span></span>
               <span class="token attr-name">onChange</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>handleChange<span class="token punctuation">}</span></span> <span class="token punctuation">/&gt;</span></span><span class="token plain-text">
      </span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>fieldset</span><span class="token punctuation">&gt;</span></span>
    <span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span>


<span class="token comment">// 父组件 - 计算器</span>
<span class="token keyword">class</span> <span class="token class-name">Calculator</span> <span class="token keyword">extends</span> <span class="token class-name">React<span class="token punctuation">.</span>Component</span> <span class="token punctuation">{</span>
  <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">props</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">super</span><span class="token punctuation">(</span>props<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 接收父组件传入props</span>
    
    <span class="token comment">// 绑定事件回调，并修正this</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span>handleCelsiusChange <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">handleCelsiusChange</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span>handleFahrenheitChange <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">handleFahrenheitChange</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment">// 创建初始状态值</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span>state <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token literal-property property">temperature</span><span class="token operator">:</span> <span class="token string">''</span><span class="token punctuation">,</span> <span class="token literal-property property">scale</span><span class="token operator">:</span> <span class="token string">'c'</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
	
  <span class="token comment">// 处理`摄氏度`变更</span>
  <span class="token function">handleCelsiusChange</span><span class="token punctuation">(</span><span class="token parameter">temperature</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// temperature接收到子组件传来的参数，并通过setState修改状态</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">setState</span><span class="token punctuation">(</span><span class="token punctuation">{</span><span class="token literal-property property">scale</span><span class="token operator">:</span> <span class="token string">'c'</span><span class="token punctuation">,</span> temperature<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
	
  <span class="token comment">// 处理`华氏度`变更</span>
  <span class="token function">handleFahrenheitChange</span><span class="token punctuation">(</span><span class="token parameter">temperature</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// temperature接收到子组件传来的参数，并通过setState修改状态</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">setState</span><span class="token punctuation">(</span><span class="token punctuation">{</span><span class="token literal-property property">scale</span><span class="token operator">:</span> <span class="token string">'f'</span><span class="token punctuation">,</span> temperature<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
	
  <span class="token comment">// 渲染函数（每当state改变都会调用）</span>
  <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// 取得当前state下的值</span>
    <span class="token keyword">const</span> scale <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>state<span class="token punctuation">.</span>scale<span class="token punctuation">;</span>
    <span class="token keyword">const</span> temperature <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span>state<span class="token punctuation">.</span>temperature<span class="token punctuation">;</span>
    
    <span class="token comment">// 根据scale值取得相应的温度数据</span>
    <span class="token keyword">const</span> celsius <span class="token operator">=</span> scale <span class="token operator">===</span> <span class="token string">'f'</span> <span class="token operator">?</span> <span class="token function">tryConvert</span><span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> toCelsius<span class="token punctuation">)</span> <span class="token operator">:</span> temperature<span class="token punctuation">;</span>
    <span class="token keyword">const</span> fahrenheit <span class="token operator">=</span> scale <span class="token operator">===</span> <span class="token string">'c'</span> <span class="token operator">?</span> <span class="token function">tryConvert</span><span class="token punctuation">(</span>temperature<span class="token punctuation">,</span> toFahrenheit<span class="token punctuation">)</span> <span class="token operator">:</span> temperature<span class="token punctuation">;</span>
		
    <span class="token comment">// 返回渲染的元素</span>
    <span class="token comment">// 插入子组件TemperatureInput传入相应的参数，onTemperatureChange指定为当前组件的回调函数</span>
    <span class="token keyword">return</span> <span class="token punctuation">(</span>
      <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span><span class="token punctuation">&gt;</span></span><span class="token plain-text">
        </span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span><span class="token class-name">TemperatureInput</span></span>
          <span class="token attr-name">scale</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>c<span class="token punctuation">&quot;</span></span>
          <span class="token attr-name">temperature</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span>celsius<span class="token punctuation">}</span></span>
          <span class="token attr-name">onTemperatureChange</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>handleCelsiusChange<span class="token punctuation">}</span></span> <span class="token punctuation">/&gt;</span></span><span class="token plain-text">
        </span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span><span class="token class-name">TemperatureInput</span></span>
          <span class="token attr-name">scale</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>f<span class="token punctuation">&quot;</span></span>
          <span class="token attr-name">temperature</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span>fahrenheit<span class="token punctuation">}</span></span>
          <span class="token attr-name">onTemperatureChange</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>handleFahrenheitChange<span class="token punctuation">}</span></span> <span class="token punctuation">/&gt;</span></span><span class="token plain-text">
        </span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span><span class="token class-name">BoilingVerdict</span></span>
          <span class="token attr-name">celsius</span><span class="token script language-javascript"><span class="token script-punctuation punctuation">=</span><span class="token punctuation">{</span><span class="token function">parseFloat</span><span class="token punctuation">(</span>celsius<span class="token punctuation">)</span><span class="token punctuation">}</span></span> <span class="token punctuation">/&gt;</span></span><span class="token plain-text">
      </span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
    <span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

<span class="token comment">// 渲染DOM</span>
ReactDOM<span class="token punctuation">.</span><span class="token function">render</span><span class="token punctuation">(</span>
  <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span><span class="token class-name">Calculator</span></span> <span class="token punctuation">/&gt;</span></span><span class="token punctuation">,</span>
  document<span class="token punctuation">.</span><span class="token function">getElementById</span><span class="token punctuation">(</span><span class="token string">'root'</span><span class="token punctuation">)</span>
<span class="token punctuation">)</span><span class="token punctuation">;</span>
</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><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span 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class="line-number">125</span><br><span class="line-number">126</span><br><span class="line-number">127</span><br></div></div><p><a href="https://codepen.io/gaearon/pen/WZpxpz?editors=0010" target="_blank" rel="noopener noreferrer"><strong>在 CodePen 上尝试</strong><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 class="custom-block note"><p class="custom-block-title">笔记</p> <ol><li>父组件给所有子组件传入state的值</li> <li>子组件修改值时调用父组件的方法并把值传出</li> <li>父组件接收到值之后修改state</li> <li>state被修改之后重新执行render函数，并回到第1步</li></ol></div> <h3 id="小结"><a href="#小结" class="header-anchor">#</a> 小结</h3> <ul><li><p>任何可变数据应当只有一个相对应的唯一“数据源”</p> <ul><li>通常，state 都是首先添加到需要渲染数据的组件中去</li> <li>然后，如果其他组件也需要这个 state，那么你可以将它提升至这些组件的最近共同父组件中</li> <li>你应当依靠<a href="https://zh-hans.reactjs.org/docs/state-and-lifecycle.html#the-data-flows-down" target="_blank" rel="noopener noreferrer">自上而下的数据流<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>，而不是尝试在不同组件间同步 state。</li></ul></li> <li><p>“存在”于组件中的任何 state，仅有组件自己能够修改它</p></li> <li><p>如果某些数据可以由 props 或 state 推导得出，那么它就不应该存在于 state 中。（如上例中，经过tryConvert方法转换的后的值。）</p></li></ul> <h3 id="react开发者工具-debug"><a href="#react开发者工具-debug" class="header-anchor">#</a> React开发者工具（debug）</h3> <p>当你在 UI 中发现错误时，可以使用 <a href="https://github.com/facebook/react/tree/master/packages/react-devtools" target="_blank" rel="noopener noreferrer">React 开发者工具<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> 来检查问题组件的 props，并且按照组件树结构逐级向上搜寻，直到定位到负责更新 state 的那个组件。</p></div></div>  <div class="page-edit"><div class="edit-link"><a href="https://github.com/heBody/blog/edit/master/docs/《React》笔记/01.核心概念/09.状态提升.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="tags"><a href="/blog/tags/?tag=React" title="标签">#React</a></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/002db7/" class="page-nav-centre page-nav-centre-prev"><div 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