mirror of
https://github.com/facebook/react.git
synced 2025-11-01 09:12:30 +00:00
Christopher Chedeau
593 lines
33 KiB
HTML
593 lines
33 KiB
HTML
<!DOCTYPE html>
|
||
<!--[if IE]><![endif]-->
|
||
<html>
|
||
<head>
|
||
<meta charset="utf-8">
|
||
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
|
||
<title>复合组件 | React</title>
|
||
<meta name="viewport" content="width=device-width">
|
||
<meta property="og:title" content="复合组件 | React">
|
||
<meta property="og:type" content="website">
|
||
<meta property="og:url" content="http://facebook.github.io/react/docs/multiple-components-zh-CN.html">
|
||
<meta property="og:image" content="http://facebook.github.io/react/img/logo_og.png">
|
||
<meta property="og:description" content="A JavaScript library for building user interfaces">
|
||
<meta property="fb:app_id" content="623268441017527">
|
||
|
||
<link rel="shortcut icon" href="/react/favicon.ico">
|
||
<link rel="alternate" type="application/rss+xml" title="React" href="http://facebook.github.io/react/feed.xml">
|
||
|
||
<link rel="stylesheet" href="/react/css/syntax.css">
|
||
<link rel="stylesheet" href="/react/css/codemirror.css">
|
||
<link rel="stylesheet" href="/react/css/react.css">
|
||
|
||
<script type="text/javascript" src="//use.typekit.net/vqa1hcx.js"></script>
|
||
<script type="text/javascript">try{Typekit.load();}catch(e){}</script>
|
||
|
||
<!--[if lte IE 8]>
|
||
<script type="text/javascript" src="/react/js/html5shiv.min.js"></script>
|
||
<script type="text/javascript" src="/react/js/es5-shim.min.js"></script>
|
||
<script type="text/javascript" src="/react/js/es5-sham.min.js"></script>
|
||
<![endif]-->
|
||
<script type="text/javascript" src="/react/js/codemirror.js"></script>
|
||
<script type="text/javascript" src="/react/js/javascript.js"></script>
|
||
<script type="text/javascript" src="/react/js/react.js"></script>
|
||
<script type="text/javascript" src="/react/js/JSXTransformer.js"></script>
|
||
<script type="text/javascript" src="/react/js/live_editor.js"></script>
|
||
<script type="text/javascript" src="/react/js/showdown.js"></script>
|
||
</head>
|
||
<body>
|
||
|
||
<div class="container">
|
||
|
||
<div class="nav-main">
|
||
<div class="wrap">
|
||
<a class="nav-home" href="/react/index.html">
|
||
<img class="nav-logo" src="/react/img/logo.svg" width="36" height="36">
|
||
React
|
||
</a>
|
||
<ul class="nav-site">
|
||
<li><a href="/react/docs/getting-started.html" class="active">docs</a></li>
|
||
<li><a href="/react/support.html">support</a></li>
|
||
<li><a href="/react/downloads.html">download</a></li>
|
||
<li><a href="/react/blog/">blog</a></li>
|
||
<li><a href="http://github.com/facebook/react">github</a>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
|
||
|
||
|
||
<section class="content wrap documentationContent">
|
||
<div class="nav-docs">
|
||
<!-- Docs Nav -->
|
||
|
||
<div class="nav-docs-section">
|
||
<h3>Quick Start</h3>
|
||
<ul>
|
||
|
||
<li>
|
||
<a href="/react/docs/getting-started.html">Getting Started</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/tutorial.html">Tutorial</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/thinking-in-react.html">Thinking in React</a>
|
||
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
|
||
<div class="nav-docs-section">
|
||
<h3>Community Resources</h3>
|
||
<ul>
|
||
|
||
<li>
|
||
<a href="/react/docs/videos.html">Videos</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/complementary-tools.html">Complementary Tools</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/examples.html">Examples</a>
|
||
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
|
||
<div class="nav-docs-section">
|
||
<h3>Guides</h3>
|
||
<ul>
|
||
|
||
<li>
|
||
<a href="/react/docs/why-react.html">Why React?</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/displaying-data.html">Displaying Data</a>
|
||
|
||
<ul>
|
||
|
||
<li>
|
||
<a href="/react/docs/jsx-in-depth.html">JSX in Depth</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/jsx-spread.html">JSX Spread Attributes</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/jsx-gotchas.html">JSX Gotchas</a>
|
||
</li>
|
||
|
||
</ul>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/interactivity-and-dynamic-uis.html">Interactivity and Dynamic UIs</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/multiple-components.html">Multiple Components</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/reusable-components.html">Reusable Components</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/transferring-props.html">Transferring Props</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/forms.html">Forms</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/working-with-the-browser.html">Working With the Browser</a>
|
||
|
||
<ul>
|
||
|
||
<li>
|
||
<a href="/react/docs/more-about-refs.html">More About Refs</a>
|
||
</li>
|
||
|
||
</ul>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/tooling-integration.html">Tooling Integration</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/addons.html">Add-Ons</a>
|
||
|
||
<ul>
|
||
|
||
<li>
|
||
<a href="/react/docs/animation.html">Animation</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/two-way-binding-helpers.html">Two-Way Binding Helpers</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/class-name-manipulation.html">Class Name Manipulation</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/test-utils.html">Test Utilities</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/clone-with-props.html">Cloning Components</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/update.html">Immutability Helpers</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/pure-render-mixin.html">PureRenderMixin</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/perf.html">Performance Tools</a>
|
||
</li>
|
||
|
||
</ul>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/advanced-performance.html">Advanced Performance</a>
|
||
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
|
||
<div class="nav-docs-section">
|
||
<h3>Reference</h3>
|
||
<ul>
|
||
|
||
<li>
|
||
<a href="/react/docs/top-level-api.html">Top-Level API</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/component-api.html">Component API</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/component-specs.html">Component Specs and Lifecycle</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/tags-and-attributes.html">Supported Tags and Attributes</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/events.html">Event System</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/dom-differences.html">DOM Differences</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/special-non-dom-attributes.html">Special Non-DOM Attributes</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/reconciliation.html">Reconciliation</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/docs/glossary.html">React (Virtual) DOM Terminology</a>
|
||
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
|
||
<div class="nav-docs-section">
|
||
<h3>Flux</h3>
|
||
<ul>
|
||
|
||
<li>
|
||
<a href="http://facebook.github.io/flux/docs/overview.html">Flux Overview</a>
|
||
|
||
</li>
|
||
|
||
<li>
|
||
<a href="http://facebook.github.io/flux/docs/todo-list.html">Flux TodoMVC Tutorial</a>
|
||
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
|
||
|
||
<!-- Tips Nav -->
|
||
|
||
<div class="nav-docs-section">
|
||
<h3>Tips</h3>
|
||
<ul>
|
||
|
||
<li>
|
||
<a href="/react/tips/introduction.html">Introduction</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/inline-styles.html">Inline Styles</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/if-else-in-JSX.html">If-Else in JSX</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/self-closing-tag.html">Self-Closing Tag</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/maximum-number-of-jsx-root-nodes.html">Maximum Number of JSX Root Nodes</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/style-props-value-px.html">Shorthand for Specifying Pixel Values in style props</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/children-props-type.html">Type of the Children props</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/controlled-input-null-value.html">Value of null for Controlled Input</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/componentWillReceiveProps-not-triggered-after-mounting.html">componentWillReceiveProps Not Triggered After Mounting</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/props-in-getInitialState-as-anti-pattern.html">Props in getInitialState Is an Anti-Pattern</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/dom-event-listeners.html">DOM Event Listeners in a Component</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/initial-ajax.html">Load Initial Data via AJAX</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/false-in-jsx.html">False in JSX</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/communicate-between-components.html">Communicate Between Components</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/expose-component-functions.html">Expose Component Functions</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/references-to-components.html">References to Components</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/children-undefined.html">this.props.children undefined</a>
|
||
</li>
|
||
|
||
<li>
|
||
<a href="/react/tips/use-react-with-other-libraries.html">Use React with Other Libraries</a>
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
|
||
</div>
|
||
|
||
|
||
<div class="inner-content">
|
||
<h1>
|
||
复合组件
|
||
<a class="edit-page-link" href="https://github.com/facebook/react/tree/master/docs/docs/04-multiple-components.zh-CN.md" target="_blank">Edit on GitHub</a>
|
||
</h1>
|
||
<div class="subHeader"></div>
|
||
|
||
<p>目前为止，我们已经学了如何用单个组件来展示数据和处理用户输入。下一步让我们来体验 React 最激动人心的特性之一：可组合性（composability）。</p>
|
||
<h2><a class="anchor" name=""></a>动机：关注分离 <a class="hash-link" href="#">#</a></h2>
|
||
<p>通过复用那些接口定义良好的组件来开发新的模块化组件，我们得到了与使用函数和类相似的好处。具体来说就是能够通过开发简单的组件把程序的<em>不同关注面分离</em>。如果为程序开发一套自定义的组件库，那么就能以最适合业务场景的方式来展示你的用户界面。</p>
|
||
<h2><a class="anchor" name=""></a>组合实例 <a class="hash-link" href="#">#</a></h2>
|
||
<p>一起来使用 Facebook Graph API 开发显示个人图片和用户名的简单 Avatar 组件吧。</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">Avatar</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</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="k">return</span> <span class="p">(</span>
|
||
<span class="o"><</span><span class="nx">div</span><span class="o">></span>
|
||
<span class="o"><</span><span class="nx">ProfilePic</span> <span class="nx">username</span><span class="o">=</span><span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">username</span><span class="p">}</span> <span class="o">/></span>
|
||
<span class="o"><</span><span class="nx">ProfileLink</span> <span class="nx">username</span><span class="o">=</span><span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">username</span><span class="p">}</span> <span class="o">/></span>
|
||
<span class="o"><</span><span class="err">/div></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
|
||
<span class="kd">var</span> <span class="nx">ProfilePic</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</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="k">return</span> <span class="p">(</span>
|
||
<span class="o"><</span><span class="nx">img</span> <span class="nx">src</span><span class="o">=</span><span class="p">{</span><span class="s1">'http://graph.facebook.com/'</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">username</span> <span class="o">+</span> <span class="s1">'/picture'</span><span class="p">}</span> <span class="o">/></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
|
||
<span class="kd">var</span> <span class="nx">ProfileLink</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</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="k">return</span> <span class="p">(</span>
|
||
<span class="o"><</span><span class="nx">a</span> <span class="nx">href</span><span class="o">=</span><span class="p">{</span><span class="s1">'http://www.facebook.com/'</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">username</span><span class="p">}</span><span class="o">></span>
|
||
<span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">username</span><span class="p">}</span>
|
||
<span class="o"><</span><span class="err">/a></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
|
||
<span class="nx">React</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span>
|
||
<span class="o"><</span><span class="nx">Avatar</span> <span class="nx">username</span><span class="o">=</span><span class="s2">"pwh"</span> <span class="o">/></span><span class="p">,</span>
|
||
<span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">'example'</span><span class="p">)</span>
|
||
<span class="p">);</span>
|
||
</code></pre></div><h2><a class="anchor" name=""></a>从属关系 <a class="hash-link" href="#">#</a></h2>
|
||
<p>上面例子中，<code>Avatar</code> 拥有 <code>ProfilePic</code> 和 <code>ProfileLink</code> 的实例。<code>拥有者</code> 就是给其它组件设置 <code>props</code> 的那个组件。更正式地说，
|
||
如果组件 <code>Y</code> 在 <code>render()</code> 方法是创建了组件 <code>X</code>，那么 <code>Y</code> 就拥有 <code>X</code>。上面讲过，组件不能修改自身的 <code>props</code> - 它们总是与它们拥有者设置的保持一致。这是保持用户界面一致性的关键性原则。</p>
|
||
|
||
<p>把从属关系与父子关系加以区别至关重要。从属关系是 React 特有的，而父子关系简单来讲就是DOM 里的标签的关系。在上一个例子中，<code>Avatar</code> 拥有 <code>div</code>、<code>ProfilePic</code> 和 <code>ProfileLink</code> 实例，<code>div</code> 是 <code>ProfilePic</code> 和 <code>ProfileLink</code> 实例的<strong>父级</strong>（但不是拥有者）。</p>
|
||
<h2><a class="anchor" name=""></a>子级 <a class="hash-link" href="#">#</a></h2>
|
||
<p>实例化 React 组件时，你可以在开始标签和结束标签之间引用在React 组件或者Javascript 表达式：</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">Parent</span><span class="o">><</span><span class="nx">Child</span> <span class="o">/><</span><span class="err">/Parent></span>
|
||
</code></pre></div>
|
||
<p><code>Parent</code> 能通过专门的 <code>this.props.children</code> props 读取子级。<strong><code>this.props.children</code> 是一个不透明的数据结构：</strong> 通过 <a href="/react/docs/top-level-api.html#react.children">React.Children 工具类</a> 来操作。</p>
|
||
<h3><a class="anchor" name="reconciliation"></a>子级校正（Reconciliation） <a class="hash-link" href="#reconciliation">#</a></h3>
|
||
<p><strong>校正就是每次 render 方法调用后 React 更新 DOM 的过程。</strong> 一般情况下，子级会根据它们被渲染的顺序来做校正。例如，下面代码描述了两次渲染的过程：</p>
|
||
<div class="highlight"><pre><code class="language-html" data-lang="html">// 第一次渲染
|
||
<span class="nt"><Card></span>
|
||
<span class="nt"><p></span>Paragraph 1<span class="nt"></p></span>
|
||
<span class="nt"><p></span>Paragraph 2<span class="nt"></p></span>
|
||
<span class="nt"></Card></span>
|
||
// 第二次渲染
|
||
<span class="nt"><Card></span>
|
||
<span class="nt"><p></span>Paragraph 2<span class="nt"></p></span>
|
||
<span class="nt"></Card></span>
|
||
</code></pre></div>
|
||
<p>直观来看，只是删除了<code><p>Paragraph 1</p></code>。事实上，React 先更新第一个子级的内容，然后删除最后一个组件。React 是根据子级的<em>顺序</em>来校正的。</p>
|
||
<h3><a class="anchor" name=""></a>子组件状态管理 <a class="hash-link" href="#">#</a></h3>
|
||
<p>对于大多数组件，这没什么大碍。但是，对于使用 <code>this.state</code> 来在多次渲染过程中里维持数据的状态化组件，这样做潜在很多问题。</p>
|
||
|
||
<p>多数情况下，可以通过隐藏组件而不是删除它们来绕过这些问题。</p>
|
||
<div class="highlight"><pre><code class="language-html" data-lang="html">// 第一次渲染
|
||
<span class="nt"><Card></span>
|
||
<span class="nt"><p></span>Paragraph 1<span class="nt"></p></span>
|
||
<span class="nt"><p></span>Paragraph 2<span class="nt"></p></span>
|
||
<span class="nt"></Card></span>
|
||
// 第二次渲染
|
||
<span class="nt"><Card></span>
|
||
<span class="nt"><p</span> <span class="na">style=</span><span class="s">{{display:</span> <span class="err">'</span><span class="na">none</span><span class="err">'}}</span><span class="nt">></span>Paragraph 1<span class="nt"></p></span>
|
||
<span class="nt"><p></span>Paragraph 2<span class="nt"></p></span>
|
||
<span class="nt"></Card></span>
|
||
</code></pre></div><h3><a class="anchor" name=""></a>动态子级 <a class="hash-link" href="#">#</a></h3>
|
||
<p>如果子组件位置会改变（如在搜索结果中）或者有新组件添加到列表开头（如在流中）情况会变得更加复杂。如果子级要在多个渲染阶段保持自己的特征和状态，在这种情况下，你可以通过给子级设置惟一标识的 <code>key</code> 来区分。</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
||
<span class="kd">var</span> <span class="nx">results</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">results</span><span class="p">;</span>
|
||
<span class="k">return</span> <span class="p">(</span>
|
||
<span class="o"><</span><span class="nx">ol</span><span class="o">></span>
|
||
<span class="p">{</span><span class="nx">results</span><span class="p">.</span><span class="nx">map</span><span class="p">(</span><span class="kd">function</span><span class="p">(</span><span class="nx">result</span><span class="p">)</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="o"><</span><span class="nx">li</span> <span class="nx">key</span><span class="o">=</span><span class="p">{</span><span class="nx">result</span><span class="p">.</span><span class="nx">id</span><span class="p">}</span><span class="o">></span><span class="p">{</span><span class="nx">result</span><span class="p">.</span><span class="nx">text</span><span class="p">}</span><span class="o"><</span><span class="err">/li>;</span>
|
||
<span class="p">})}</span>
|
||
<span class="o"><</span><span class="err">/ol></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
</code></pre></div>
|
||
<p>当 React 校正带有 key 的子级时，它会确保它们被重新排序（而不是破坏）或者删除（而不是重用）。
|
||
<code>务必</code> 把 <code>key</code> 添加到子级数组里组件本身上，而不是每个子级内部最外层 HTML 上：</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="c1">// 错误！</span>
|
||
<span class="kd">var</span> <span class="nx">ListItemWrapper</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</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="k">return</span> <span class="o"><</span><span class="nx">li</span> <span class="nx">key</span><span class="o">=</span><span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">data</span><span class="p">.</span><span class="nx">id</span><span class="p">}</span><span class="o">></span><span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">data</span><span class="p">.</span><span class="nx">text</span><span class="p">}</span><span class="o"><</span><span class="err">/li>;</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
<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>
|
||
<span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="p">(</span>
|
||
<span class="o"><</span><span class="nx">ul</span><span class="o">></span>
|
||
<span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">results</span><span class="p">.</span><span class="nx">map</span><span class="p">(</span><span class="kd">function</span><span class="p">(</span><span class="nx">result</span><span class="p">)</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="o"><</span><span class="nx">ListItemWrapper</span> <span class="nx">data</span><span class="o">=</span><span class="p">{</span><span class="nx">result</span><span class="p">}</span><span class="o">/></span><span class="p">;</span>
|
||
<span class="p">})}</span>
|
||
<span class="o"><</span><span class="err">/ul></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
|
||
<span class="c1">// 正确 :)</span>
|
||
<span class="kd">var</span> <span class="nx">ListItemWrapper</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</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="k">return</span> <span class="o"><</span><span class="nx">li</span><span class="o">></span><span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">data</span><span class="p">.</span><span class="nx">text</span><span class="p">}</span><span class="o"><</span><span class="err">/li>;</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
<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>
|
||
<span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="p">(</span>
|
||
<span class="o"><</span><span class="nx">ul</span><span class="o">></span>
|
||
<span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">results</span><span class="p">.</span><span class="nx">map</span><span class="p">(</span><span class="kd">function</span><span class="p">(</span><span class="nx">result</span><span class="p">)</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="o"><</span><span class="nx">ListItemWrapper</span> <span class="nx">key</span><span class="o">=</span><span class="p">{</span><span class="nx">result</span><span class="p">.</span><span class="nx">id</span><span class="p">}</span> <span class="nx">data</span><span class="o">=</span><span class="p">{</span><span class="nx">result</span><span class="p">}</span><span class="o">/></span><span class="p">;</span>
|
||
<span class="p">})}</span>
|
||
<span class="o"><</span><span class="err">/ul></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
</code></pre></div>
|
||
<p>也可以传递 object 来做有 key 的子级。object 的 key 会被当作每个组件的 <code>key</code>。但是一定要牢记 JavaScript 并不总是保证属性的顺序会被保留。实际情况下浏览器一般会保留属性的顺序，<strong>除了</strong> 使用 32位无符号数字做为 key 的属性。数字型属性会按大小排序并且排在其它属性前面。一旦发生这种情况，React 渲染组件的顺序就是混乱。可能在 key 前面加一个字符串前缀来避免：</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
||
<span class="kd">var</span> <span class="nx">items</span> <span class="o">=</span> <span class="p">{};</span>
|
||
|
||
<span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">results</span><span class="p">.</span><span class="nx">forEach</span><span class="p">(</span><span class="kd">function</span><span class="p">(</span><span class="nx">result</span><span class="p">)</span> <span class="p">{</span>
|
||
<span class="c1">// 如果 result.id 看起来是一个数字（比如短哈希），那么</span>
|
||
<span class="c1">// 对象字面量的顺序就得不到保证。这种情况下，需要添加前缀</span>
|
||
<span class="c1">// 来确保 key 是字符串。</span>
|
||
<span class="nx">items</span><span class="p">[</span><span class="s1">'result-'</span> <span class="o">+</span> <span class="nx">result</span><span class="p">.</span><span class="nx">id</span><span class="p">]</span> <span class="o">=</span> <span class="o"><</span><span class="nx">li</span><span class="o">></span><span class="p">{</span><span class="nx">result</span><span class="p">.</span><span class="nx">text</span><span class="p">}</span><span class="o"><</span><span class="err">/li>;</span>
|
||
<span class="p">});</span>
|
||
|
||
<span class="k">return</span> <span class="p">(</span>
|
||
<span class="o"><</span><span class="nx">ol</span><span class="o">></span>
|
||
<span class="p">{</span><span class="nx">items</span><span class="p">}</span>
|
||
<span class="o"><</span><span class="err">/ol></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
</code></pre></div><h2><a class="anchor" name=""></a>数据流 <a class="hash-link" href="#">#</a></h2>
|
||
<p>React 里，数据通过上面介绍过的 <code>props</code> 从拥有者流向归属者。这就是高效的单向数据绑定(one-way data binding)：拥有者通过它的 <code>props</code> 或 <code>state</code> 计算出一些值，并把这些值绑定到它们拥有的组件的 props 上。因为这个过程会递归地调用，所以数据变化会自动在所有被使用的地方自动反映出来。</p>
|
||
<h2><a class="anchor" name=""></a>性能提醒 <a class="hash-link" href="#">#</a></h2>
|
||
<p>你或许会担心如果一个拥有者有大量子级时，对于数据变化做出响应非常耗费性能。值得庆幸的是执行 JavaScript 非常的快，而且 <code>render()</code> 方法一般比较简单，所以在大部分应用里这样做速度极快。此外，性能的瓶颈大多是因为 DOM 更新，而非 JS 执行，而且 React 会通过批量更新和变化检测来优化性能。</p>
|
||
|
||
<p>但是，有时候需要做细粒度的性能控制。这种情况下，可以重写 <code>shouldComponentUpdate()</code> 方法返回 false 来让 React 跳过对子树的处理。参考 <a href="/react/docs/component-specs.html">React reference docs</a> 了解更多。</p>
|
||
|
||
<blockquote>
|
||
<p>注意：</p>
|
||
|
||
<p>如果在数据变化时让 <code>shouldComponentUpdate()</code> 返回 false，React 就不能保证用户界面同步。当使用它的时候一定确保你清楚到底做了什么，并且只在遇到明显性能问题的时候才使用它。不要低估 JavaScript 的速度，DOM 操作通常才是慢的原因。</p>
|
||
</blockquote>
|
||
|
||
|
||
<div class="docs-prevnext">
|
||
|
||
<a class="docs-prev" href="/react/docs/interactivity-and-dynamic-uis-zh-CN.html">← Prev</a>
|
||
|
||
|
||
<a class="docs-next" href="/react/docs/reusable-components-zh-CN.html">Next →</a>
|
||
|
||
</div>
|
||
</div>
|
||
</section>
|
||
|
||
|
||
<footer class="wrap">
|
||
<div class="left">
|
||
A Facebook & Instagram collaboration.<br>
|
||
<a href="/react/acknowledgements.html">Acknowledgements</a>
|
||
</div>
|
||
<div class="right">
|
||
© 2013–2015 Facebook Inc.<br>
|
||
Documentation licensed under <a href="http://creativecommons.org/licenses/by/4.0/">CC BY 4.0</a>.
|
||
</div>
|
||
</footer>
|
||
</div>
|
||
<div id="fb-root"></div>
|
||
|
||
<script>
|
||
(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
|
||
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
|
||
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
|
||
})(window,document,'script','//www.google-analytics.com/analytics.js','ga');
|
||
ga('create', 'UA-41298772-1', 'facebook.github.io');
|
||
ga('send', 'pageview');
|
||
|
||
!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="https://platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");
|
||
|
||
(function(d, s, id) {
|
||
var js, fjs = d.getElementsByTagName(s)[0];
|
||
if (d.getElementById(id)) return;
|
||
js = d.createElement(s); js.id = id;
|
||
js.src = "//connect.facebook.net/en_US/all.js#xfbml=1&appId=623268441017527";
|
||
fjs.parentNode.insertBefore(js, fjs);
|
||
}(document, 'script', 'facebook-jssdk'));
|
||
</script>
|
||
</body>
|
||
</html>
|