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593 lines
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HTML
593 lines
28 KiB
HTML
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<a href="/react/tips/introduction.html">Introduction</a>
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<a href="/react/tips/maximum-number-of-jsx-root-nodes.html">Maximum Number of JSX Root Nodes</a>
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<a href="/react/tips/style-props-value-px.html">Shorthand for Specifying Pixel Values in style props</a>
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<a href="/react/tips/children-props-type.html">Type of the Children props</a>
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<a href="/react/tips/controlled-input-null-value.html">Value of null for Controlled Input</a>
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<a href="/react/tips/componentWillReceiveProps-not-triggered-after-mounting.html">componentWillReceiveProps Not Triggered After Mounting</a>
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<a href="/react/tips/props-in-getInitialState-as-anti-pattern.html">Props in getInitialState Is an Anti-Pattern</a>
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<li>
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<a href="/react/tips/dom-event-listeners.html">DOM Event Listeners in a Component</a>
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<a href="/react/tips/initial-ajax.html">Load Initial Data via AJAX</a>
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<a href="/react/tips/false-in-jsx.html">False in JSX</a>
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<a href="/react/tips/communicate-between-components.html">Communicate Between Components</a>
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<a href="/react/tips/expose-component-functions.html">Expose Component Functions</a>
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<a href="/react/tips/children-undefined.html">this.props.children undefined</a>
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<li>
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<a href="/react/tips/use-react-with-other-libraries.html">Use React with Other Libraries</a>
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<li>
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<a href="/react/tips/dangerously-set-inner-html.html">Dangerously Set innerHTML</a>
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</ul>
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</div>
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</div>
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<div class="inner-content">
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<h1>
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组件的规范和生命周期
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<a class="edit-page-link" href="https://github.com/facebook/react/tree/master/docs/docs/ref-03-component-specs.zh-CN.md" target="_blank">Edit on GitHub</a>
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</h1>
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<div class="subHeader"></div>
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<h2><a class="anchor" name="specifications"></a>组件规范(Specifications) <a class="hash-link" href="#specifications">#</a></h2>
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<p>当调用 <code>React.createClass()</code> 创建一个组件类时,你应该提供一个包含有 <code>render</code> 方法以及可选的其他生命周期方法的 规范(Specifications)对象.</p>
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<blockquote>
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<p>注意:</p>
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<p>同样可以使用单纯的 JavaScript 类作为组件类. 这些类可以实现大多数相同的方法,虽然有一些不同.更多关于不同的信息,请阅读我们关于<a href="/react/docs/reusable-components.html#es6-classes">ES6 classes</a>的文档.</p>
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</blockquote>
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<h3><a class="anchor" name="render"></a>render <a class="hash-link" href="#render">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="nx">ReactElement</span> <span class="nx">render</span><span class="p">()</span>
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</code></pre></div>
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<p><code>render()</code> 是必须的</p>
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<p>当被调用时,它应该检查 <code>this.props</code> 和 <code>this.state</code> 并返回单个子元素.这个子元素即可以是一个 对原生DOM的虚拟表达(比如 <code><div /></code> 或 <code>React.DOM.div()</code>)也可以是其他你自定义的复合组件.</p>
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<p>你也可以返回 <code>null</code> 或 <code>false</code> 来指示你不想要任何东西被渲染.幕后,React 渲染一个 <code><noscript></code> tag 来与我们当前的diffing算法协同工作.当返回 <code>null</code> 或 <code>false</code> ,<code>ReactDOM.findDOMNode(this)</code> 会返回 <code>null</code>.</p>
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<p><code>render()</code> 函数应该是纯净的,意味着它不改变组件的状态,它在每次调用时返回相同的结果,并且它不读和写 DOM 或者其他方式与浏览器互动(例如,使用 <code>setTimeout</code>).如果你需要与浏览器互动,在 <code>componentDidMount()</code> 里执行你的工作,或者其他生命周期方法里.保持 <code>render()</code> 纯净使服务器渲染更实用并且让组件更容易被思考.</p>
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<p>### getInitialState</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="nx">object</span> <span class="nx">getInitialState</span><span class="p">()</span>
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</code></pre></div>
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<p>当组件被挂载时调用一次.返回值会被用作为 <code>this.state</code> 的初始值.</p>
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<h3><a class="anchor" name="getdefaultprops"></a>getDefaultProps <a class="hash-link" href="#getdefaultprops">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="nx">object</span> <span class="nx">getDefaultProps</span><span class="p">()</span>
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</code></pre></div>
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<p>在类被创建时调用一次并被缓存.在这个mapping里的值会被设置给 <code>this.props</code> 如果父组件没有指定对应的 prop (例如 使用一个 <code>in</code> 检查).</p>
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<p>这个方法在任何实例被创建之前调用,因此不能依赖于 <code>this.props</code>.另外,小心,任何被 <code>getDefaultProps()</code>返回的复杂对象会被跨实例共享,而不是被拷贝.</p>
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<h3><a class="anchor" name="proptypes"></a>propTypes <a class="hash-link" href="#proptypes">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="nx">object</span> <span class="nx">propTypes</span>
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</code></pre></div>
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<p><code>propTypes</code> 对象允许你验证传递到你的组建的 props.更多关于 <code>propTypes</code> 的信息,见 <a href="/react/docs/reusable-components.html">Reusable Components</a>.</p>
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<h3><a class="anchor" name="mixins"></a>mixins <a class="hash-link" href="#mixins">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="nx">array</span> <span class="nx">mixins</span>
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</code></pre></div>
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<p><code>mixins</code> 数组允许你用 mixins 来在多个组件间共享行为.更多关于 mixins 的信息,见 <a href="/react/docs/reusable-components.html">Reusable Components</a>.</p>
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<h3><a class="anchor" name="statics"></a>statics <a class="hash-link" href="#statics">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="nx">object</span> <span class="nx">statics</span>
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</code></pre></div>
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<p><code>statics</code> 对象允许你定义可以在组件类上调用的静态方法.例如:</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">MyComponent</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span>
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<span class="nx">statics</span><span class="o">:</span> <span class="p">{</span>
|
|
<span class="nx">customMethod</span><span class="o">:</span> <span class="kd">function</span><span class="p">(</span><span class="nx">foo</span><span class="p">)</span> <span class="p">{</span>
|
|
<span class="k">return</span> <span class="nx">foo</span> <span class="o">===</span> <span class="s1">'bar'</span><span class="p">;</span>
|
|
<span class="p">}</span>
|
|
<span class="p">},</span>
|
|
<span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
|
<span class="p">}</span>
|
|
<span class="p">});</span>
|
|
|
|
<span class="nx">MyComponent</span><span class="p">.</span><span class="nx">customMethod</span><span class="p">(</span><span class="s1">'bar'</span><span class="p">);</span> <span class="c1">// true</span>
|
|
</code></pre></div>
|
|
<p>在这个块里定义的方法是 <em>static</em>,意味着你可以在任何组件实例被创建前运行他们,并且这些方法没有对你组件的 props 或 state 的访问权.如果你在静态方法里检查props的值,把调用者作为参数传入props给静态函数.</p>
|
|
<h3><a class="anchor" name="displayname"></a>displayName <a class="hash-link" href="#displayname">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="nx">string</span> <span class="nx">displayName</span>
|
|
</code></pre></div>
|
|
<p><code>displayName</code> 字符串被用在调试信息.JSX 自动设置这个值；见 <a href="/react/docs/jsx-in-depth.html#the-transform">JSX in Depth</a>.</p>
|
|
<h2><a class="anchor" name="lifecycle-methods"></a>Lifecycle Methods <a class="hash-link" href="#lifecycle-methods">#</a></h2>
|
|
<p>多种方法在组件生命周期的特定点上被执行.</p>
|
|
<h3><a class="anchor" name="mounting-componentwillmount"></a>Mounting: componentWillMount <a class="hash-link" href="#mounting-componentwillmount">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="k">void</span> <span class="nx">componentWillMount</span><span class="p">()</span>
|
|
</code></pre></div>
|
|
<p>被调用一次,即在客户端也在服务端,在最初的渲染发生之前 立即被调用.如果你在这个方法里调用 <code>setState</code> , <code>render()</code> 将会看到更新的 state 并不论state的变化只执行一次.</p>
|
|
<h3><a class="anchor" name="mounting-componentdidmount"></a>Mounting: componentDidMount <a class="hash-link" href="#mounting-componentdidmount">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="k">void</span> <span class="nx">componentDidMount</span><span class="p">()</span>
|
|
</code></pre></div>
|
|
<p>被调用一次,只在客户端(不在服务端),在最初的渲染发生之后 立即被调用.在生命周期的这个点上,你可以访问任何对你的子级的refs (比如 访问底层的DOM表达).子组件的 <code>componentDidMount()</code> 方法在父组件之前被调用.</p>
|
|
|
|
<p>如果你想与其他 JavaScript 框架整合,用 <code>setTimeout</code> 或 <code>setInterval</code> 设置timers,或者发送 AJAX 请求,执行这些操作在此方法中.</p>
|
|
<h3><a class="anchor" name="updating-componentwillreceiveprops"></a>Updating: componentWillReceiveProps <a class="hash-link" href="#updating-componentwillreceiveprops">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="k">void</span> <span class="nx">componentWillReceiveProps</span><span class="p">(</span>
|
|
<span class="nx">object</span> <span class="nx">nextProps</span>
|
|
<span class="p">)</span>
|
|
</code></pre></div>
|
|
<p>当一个组件收到新的props时被调用.这个方法不会为最初的渲染调用.</p>
|
|
|
|
<p>使用它作为响应 prop 转换的时机(在<code>render()</code> 被用 <code>this.setState()</code> 更新state调用 之前) .旧的 props 可以通过 <code>this.props</code> 访问. 在这个函数里调用 <code>this.setState()</code> 不会触发任何额外的渲染.</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="nx">componentWillReceiveProps</span><span class="o">:</span> <span class="kd">function</span><span class="p">(</span><span class="nx">nextProps</span><span class="p">)</span> <span class="p">{</span>
|
|
<span class="k">this</span><span class="p">.</span><span class="nx">setState</span><span class="p">({</span>
|
|
<span class="nx">likesIncreasing</span><span class="o">:</span> <span class="nx">nextProps</span><span class="p">.</span><span class="nx">likeCount</span> <span class="o">></span> <span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">likeCount</span>
|
|
<span class="p">});</span>
|
|
<span class="p">}</span>
|
|
</code></pre></div>
|
|
<blockquote>
|
|
<p>注意:</p>
|
|
|
|
<p>并没有类似的 <code>componentWillReceiveState</code> 方法. 一个即将到来的 prop 转变可能会导致一个 state 变化,但是反之不是. 如果你需要实现一个对 state 变化相应的操作,使用 <code>componentWillUpdate</code>.</p>
|
|
</blockquote>
|
|
<h3><a class="anchor" name="updating-shouldcomponentupdate"></a>Updating: shouldComponentUpdate <a class="hash-link" href="#updating-shouldcomponentupdate">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kr">boolean</span> <span class="nx">shouldComponentUpdate</span><span class="p">(</span>
|
|
<span class="nx">object</span> <span class="nx">nextProps</span><span class="p">,</span> <span class="nx">object</span> <span class="nx">nextState</span>
|
|
<span class="p">)</span>
|
|
</code></pre></div>
|
|
<p>当新的props或者state被收到,在渲染前被调用.这个方法不会在最初的渲染或者 <code>forceUpdate</code> 时被调用.</p>
|
|
|
|
<p>使用此方法作为一个 <code>return false</code> 的时机,当你确定新的 props 和 state 的转换不需要组件更新时.</p>
|
|
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="nx">shouldComponentUpdate</span><span class="o">:</span> <span class="kd">function</span><span class="p">(</span><span class="nx">nextProps</span><span class="p">,</span> <span class="nx">nextState</span><span class="p">)</span> <span class="p">{</span>
|
|
<span class="k">return</span> <span class="nx">nextProps</span><span class="p">.</span><span class="nx">id</span> <span class="o">!==</span> <span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">id</span><span class="p">;</span>
|
|
<span class="p">}</span>
|
|
</code></pre></div>
|
|
<p>如果 <code>shouldComponentUpdate</code> 返回false, <code>render()</code> 会在下次state变化前被完全跳过. 另外,<code>componentWillUpdate</code> 和 <code>componentDidUpdate</code> 将不会被调用.</p>
|
|
|
|
<p>默认情况下, <code>shouldComponentUpdate</code> 总是返回 <code>true</code> 来阻止当 <code>state</code> 突变时的细微bug,但是如果你仔细的把 <code>state</code> 作为不变量对待并只从 <code>render()</code>里的 <code>props</code> 和 <code>state</code>读,你就可以用一个比较旧的props和state与他们的替换者的实现来重写 <code>shouldComponentUpdate</code>.</p>
|
|
|
|
<p>如果性能是瓶颈,尤其是随着成百上千的组件,使用 <code>shouldComponentUpdate</code> 来加速你的app.</p>
|
|
<h3><a class="anchor" name="updating-componentwillupdate"></a>Updating: componentWillUpdate <a class="hash-link" href="#updating-componentwillupdate">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="k">void</span> <span class="nx">componentWillUpdate</span><span class="p">(</span>
|
|
<span class="nx">object</span> <span class="nx">nextProps</span><span class="p">,</span> <span class="nx">object</span> <span class="nx">nextState</span>
|
|
<span class="p">)</span>
|
|
</code></pre></div>
|
|
<p>当新的props或者state被接受时,在渲染前被立即调用.这个方法不会被初始渲染调用.</p>
|
|
|
|
<p>使用这个方法作为 在更新发生前执行一些准备 的时机.</p>
|
|
|
|
<blockquote>
|
|
<p>Note:</p>
|
|
|
|
<p>你 <em>不能</em> 在这个方法里使用 <code>this.setState()</code> .如果你需要响应一个prop变化来更新state,使用 <code>componentWillReceiveProps</code> 来替代.</p>
|
|
</blockquote>
|
|
<h3><a class="anchor" name="updating-componentdidupdate"></a>Updating: componentDidUpdate <a class="hash-link" href="#updating-componentdidupdate">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="k">void</span> <span class="nx">componentDidUpdate</span><span class="p">(</span>
|
|
<span class="nx">object</span> <span class="nx">prevProps</span><span class="p">,</span> <span class="nx">object</span> <span class="nx">prevState</span>
|
|
<span class="p">)</span>
|
|
</code></pre></div>
|
|
<p>在组件的更新被刷新到DOM后立即被调用.这个方法不会被初始渲染调用.</p>
|
|
|
|
<p>使用这个方法作为 当组件被更新后在DOM上操作 的时机.</p>
|
|
<h3><a class="anchor" name="unmounting-componentwillunmount"></a>Unmounting: componentWillUnmount <a class="hash-link" href="#unmounting-componentwillunmount">#</a></h3><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="k">void</span> <span class="nx">componentWillUnmount</span><span class="p">()</span>
|
|
</code></pre></div>
|
|
<p>在组件被从DOM卸载 前 被立即调用.</p>
|
|
|
|
<p>在这个方法里执行一些必要的清理操作,比如无效化 timers 或者清理任何被 <code>componentDidMount</code> 创建的DOM元素.</p>
|
|
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