mirror of
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synced 2025-11-01 09:12:30 +00:00
Paul O’Shannessy
635 lines
35 KiB
HTML
635 lines
35 KiB
HTML
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
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<title>Context | React</title>
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<meta property="og:title" content="Context | React">
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React
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<!-- Docs Nav -->
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<a href="/react/docs/getting-started.html">Getting Started</a>
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<a href="/react/docs/thinking-in-react.html">Thinking in React</a>
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<h3>Guides</h3>
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<a href="/react/docs/why-react.html">Why React?</a>
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<a href="/react/docs/jsx-spread.html">JSX Spread Attributes</a>
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<a href="/react/docs/jsx-gotchas.html">JSX Gotchas</a>
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<a href="/react/docs/interactivity-and-dynamic-uis.html">Interactivity and Dynamic UIs</a>
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<a href="/react/docs/working-with-the-browser.html">Working With the Browser</a>
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<a href="/react/docs/more-about-refs.html">Refs to Components</a>
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<a href="/react/docs/tooling-integration.html">Tooling Integration</a>
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<a href="/react/docs/two-way-binding-helpers.html">Two-Way Binding Helpers</a>
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<li>
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<a href="/react/docs/test-utils.html">Test Utilities</a>
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<li>
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<a href="/react/docs/clone-with-props.html">Cloning Elements</a>
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<li>
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<a href="/react/docs/create-fragment.html">Keyed Fragments</a>
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</li>
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<li>
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<a href="/react/docs/update.html">Immutability Helpers</a>
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<li>
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<a href="/react/docs/pure-render-mixin.html">PureRenderMixin</a>
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<li>
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<a href="/react/docs/perf.html">Performance Tools</a>
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<a href="/react/docs/shallow-compare.html">Shallow Compare</a>
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<a href="/react/docs/advanced-performance.html">Advanced Performance</a>
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<a href="/react/docs/context.html">Context</a>
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<div class="nav-docs-section">
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<h3>Reference</h3>
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<ul>
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<li>
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<a href="/react/docs/top-level-api.html">Top-Level API</a>
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<li>
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<a href="/react/docs/component-api.html">Component API</a>
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</li>
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<li>
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<a href="/react/docs/component-specs.html">Component Specs and Lifecycle</a>
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</li>
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<li>
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<a href="/react/docs/tags-and-attributes.html">Supported Tags and Attributes</a>
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</li>
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<li>
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<a href="/react/docs/events.html">Event System</a>
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</li>
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<li>
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<a href="/react/docs/dom-differences.html">DOM Differences</a>
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</li>
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<li>
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<a href="/react/docs/special-non-dom-attributes.html">Special Non-DOM Attributes</a>
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</li>
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<li>
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<a href="/react/docs/reconciliation.html">Reconciliation</a>
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</li>
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<li>
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<a href="/react/docs/webcomponents.html">Web Components</a>
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</li>
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<li>
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<a href="/react/docs/glossary.html">React (Virtual) DOM Terminology</a>
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</li>
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</ul>
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</div>
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<div class="nav-docs-section">
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<h3>Flux</h3>
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<ul>
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<li>
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<a href="https://facebook.github.io/flux/docs/overview.html" class="external">Flux Overview</a>
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</li>
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<li>
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<a href="https://facebook.github.io/flux/docs/todo-list.html" class="external">Flux TodoMVC Tutorial</a>
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</li>
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</ul>
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</div>
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<!-- Tips Nav -->
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<div class="nav-docs-section">
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<h3>Tips</h3>
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<ul>
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<li>
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<a href="/react/tips/introduction.html">Introduction</a>
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</li>
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<li>
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<a href="/react/tips/inline-styles.html">Inline Styles</a>
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</li>
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<li>
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<a href="/react/tips/if-else-in-JSX.html">If-Else in JSX</a>
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</li>
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<li>
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<a href="/react/tips/self-closing-tag.html">Self-Closing Tag</a>
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</li>
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<li>
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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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</li>
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<li>
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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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</li>
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<li>
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<a href="/react/tips/children-props-type.html">Type of the Children props</a>
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</li>
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<li>
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<a href="/react/tips/controlled-input-null-value.html">Value of null for Controlled Input</a>
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</li>
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<li>
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<a href="/react/tips/componentWillReceiveProps-not-triggered-after-mounting.html">componentWillReceiveProps Not Triggered After Mounting</a>
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</li>
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<li>
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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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<li>
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<a href="/react/tips/dom-event-listeners.html">DOM Event Listeners in a Component</a>
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</li>
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<li>
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<a href="/react/tips/initial-ajax.html">Load Initial Data via AJAX</a>
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</li>
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<li>
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<a href="/react/tips/false-in-jsx.html">False in JSX</a>
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</li>
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<li>
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<a href="/react/tips/communicate-between-components.html">Communicate Between Components</a>
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</li>
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<li>
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<a href="/react/tips/expose-component-functions.html">Expose Component Functions</a>
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</li>
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<li>
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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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<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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<li>
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<a href="/react/tips/dangerously-set-inner-html.html">Dangerously Set innerHTML</a>
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</li>
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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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Context
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<a class="edit-page-link" href="https://github.com/facebook/react/tree/master/docs/docs/12-context.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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<p>React最大的优势之一是很容易从你的React组件里跟踪数据流动。当你看着一个组件，你可以很容易准确看出哪个props被传入，这让你的APP很容易推断。</p>
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<p>偶尔，你想通过组件树传递数据，而不在每一级上手工下传prop，React的 "context" 让你做到这点。</p>
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<p>＞ 注意：
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＞
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＞ Context是一个先进的实验性特性．这个 API 很可能在未来版本变化.</p>
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<blockquote>
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<p>大多数应用将不会需要用到 context. 尤其是如果你刚开始用React,你很可能不会想用 context.使用 context 将会使你的代码很难理解因为它让数据流不清晰.它类似于在你的应用里使用全局变量传递state.</p>
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<p><strong>如果你必须使用 context ,保守的使用它</strong></p>
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<p>不论你正在创建一个应用或者是库,试着分离你对 context 的使用到一个小区域,并尽可能避免直接使用 context API,以便在API变动时容易升级.</p>
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</blockquote>
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<h2><a class="anchor" name="info"></a>从树里自动传递info <a class="hash-link" href="#info">#</a></h2>
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<p>假设你有一个这样的结构:</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">Button</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">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
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<span class="k">return</span> <span class="p">(</span>
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<span class="o"><</span><span class="nx">button</span> <span class="nx">style</span><span class="o">=</span><span class="p">{{</span><span class="nx">background</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">color</span><span class="p">}}</span><span class="o">></span>
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<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">children</span><span class="p">}</span>
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<span class="o"><</span><span class="err">/button></span>
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<span class="p">);</span>
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<span class="p">}</span>
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<span class="p">});</span>
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<span class="kd">var</span> <span class="nx">Message</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">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
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<span class="k">return</span> <span class="p">(</span>
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<span class="o"><</span><span class="nx">div</span><span class="o">></span>
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<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">text</span><span class="p">}</span> <span class="o"><</span><span class="nx">Button</span> <span class="nx">color</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">color</span><span class="p">}</span><span class="o">></span><span class="nx">Delete</span><span class="o"><</span><span class="err">/Button></span>
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<span class="o"><</span><span class="err">/div></span>
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<span class="p">);</span>
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<span class="p">}</span>
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<span class="p">});</span>
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<span class="kd">var</span> <span class="nx">MessageList</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">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
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<span class="kd">var</span> <span class="nx">color</span> <span class="o">=</span> <span class="s2">"purple"</span><span class="p">;</span>
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<span class="kd">var</span> <span class="nx">children</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">messages</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">message</span><span class="p">)</span> <span class="p">{</span>
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<span class="k">return</span> <span class="o"><</span><span class="nx">Message</span> <span class="nx">text</span><span class="o">=</span><span class="p">{</span><span class="nx">message</span><span class="p">.</span><span class="nx">text</span><span class="p">}</span> <span class="nx">color</span><span class="o">=</span><span class="p">{</span><span class="nx">color</span><span class="p">}</span> <span class="o">/></span><span class="p">;</span>
|
||
<span class="p">});</span>
|
||
<span class="k">return</span> <span class="o"><</span><span class="nx">div</span><span class="o">></span><span class="p">{</span><span class="nx">children</span><span class="p">}</span><span class="o"><</span><span class="err">/div>;</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
</code></pre></div>
|
||
<p>在这里例子里,我们手工穿透一个 <code>color</code> prop 以便于恰当格式化 <code>Button</code> 和 <code>Message</code> 组件.主题是一个很好的例子,当你可能想整个子树都可以访问一部分信息时(比如color). 使用 context 我们可以自动传过这个树:</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">Button</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="hll"> <span class="nx">contextTypes</span><span class="o">:</span> <span class="p">{</span>
|
||
</span><span class="hll"> <span class="nx">color</span><span class="o">:</span> <span class="nx">React</span><span class="p">.</span><span class="nx">PropTypes</span><span class="p">.</span><span class="nx">string</span>
|
||
</span><span class="hll"> <span class="p">},</span>
|
||
</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="hll"> <span class="o"><</span><span class="nx">button</span> <span class="nx">style</span><span class="o">=</span><span class="p">{{</span><span class="nx">background</span><span class="o">:</span> <span class="k">this</span><span class="p">.</span><span class="nx">context</span><span class="p">.</span><span class="nx">color</span><span class="p">}}</span><span class="o">></span>
|
||
</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">children</span><span class="p">}</span>
|
||
<span class="o"><</span><span class="err">/button></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
|
||
<span class="kd">var</span> <span class="nx">Message</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="hll"> <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">text</span><span class="p">}</span> <span class="o"><</span><span class="nx">Button</span><span class="o">></span><span class="nx">Delete</span><span class="o"><</span><span class="err">/Button></span>
|
||
</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">MessageList</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="hll"> <span class="nx">childContextTypes</span><span class="o">:</span> <span class="p">{</span>
|
||
</span><span class="hll"> <span class="nx">color</span><span class="o">:</span> <span class="nx">React</span><span class="p">.</span><span class="nx">PropTypes</span><span class="p">.</span><span class="nx">string</span>
|
||
</span><span class="hll"> <span class="p">},</span>
|
||
</span><span class="hll"> <span class="nx">getChildContext</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
||
</span><span class="hll"> <span class="k">return</span> <span class="p">{</span><span class="nx">color</span><span class="o">:</span> <span class="s2">"purple"</span><span class="p">};</span>
|
||
</span><span class="hll"> <span class="p">},</span>
|
||
</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="kd">var</span> <span class="nx">children</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">messages</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">message</span><span class="p">)</span> <span class="p">{</span>
|
||
<span class="hll"> <span class="k">return</span> <span class="o"><</span><span class="nx">Message</span> <span class="nx">text</span><span class="o">=</span><span class="p">{</span><span class="nx">message</span><span class="p">.</span><span class="nx">text</span><span class="p">}</span> <span class="o">/></span><span class="p">;</span>
|
||
</span> <span class="p">});</span>
|
||
<span class="k">return</span> <span class="o"><</span><span class="nx">div</span><span class="o">></span><span class="p">{</span><span class="nx">children</span><span class="p">}</span><span class="o"><</span><span class="err">/div>;</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
</code></pre></div>
|
||
<p>通过添加 <code>childContextTypes</code> 和 <code>getChildContext</code> 到 <code>MessageList</code> ( context 提供),React下传信息到子树中的任何组件(在这个例子中, <code>Button</code>可以由定义 <code>contextTypes</code>来访问它).</p>
|
||
|
||
<p>如果 <code>contextTypes</code> 没有定义,那么 <code>this.context</code> 将是一个空对象.</p>
|
||
<h2><a class="anchor" name=""></a>父子耦合 <a class="hash-link" href="#">#</a></h2>
|
||
<p>Context 同样可以使你构建这样的 APT:</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">Menu</span><span class="o">></span>
|
||
<span class="o"><</span><span class="nx">MenuItem</span><span class="o">></span><span class="nx">aubergine</span><span class="o"><</span><span class="err">/MenuItem></span>
|
||
<span class="o"><</span><span class="nx">MenuItem</span><span class="o">></span><span class="nx">butternut</span> <span class="nx">squash</span><span class="o"><</span><span class="err">/MenuItem></span>
|
||
<span class="o"><</span><span class="nx">MenuItem</span><span class="o">></span><span class="nx">clementine</span><span class="o"><</span><span class="err">/MenuItem></span>
|
||
<span class="o"><</span><span class="err">/Menu></span>
|
||
</code></pre></div>
|
||
<p>通过在 <code>Menu</code> 组件下传相关的信息,每个 <code>MenuItem</code> 可以与包含他们的 <code>Menu</code> 组件沟通.</p>
|
||
|
||
<p><strong>在你用这个API构建组件以前,考虑一下是否有清晰的替代方案</strong> 我们 喜欢像这样简单的用数组传递items:</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">Menu</span> <span class="nx">items</span><span class="o">=</span><span class="p">{[</span><span class="s1">'aubergine'</span><span class="p">,</span> <span class="s1">'butternut squash'</span><span class="p">,</span> <span class="s1">'clementine'</span><span class="p">]}</span> <span class="o">/></span>
|
||
</code></pre></div>
|
||
<p>记住你同样可以在props里传递整个React组件,如果你想.</p>
|
||
<h2><a class="anchor" name="-context"></a>在生命周期方法里引用 context <a class="hash-link" href="#-context">#</a></h2>
|
||
<p>如果 <code>contextTypes</code> 在一个组件中定义,接下来的生命周期方法会收到一个额外的参数, <code>context</code> 对象:</p>
|
||
<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> <span class="nx">object</span> <span class="nx">nextContext</span>
|
||
<span class="p">)</span>
|
||
|
||
<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> <span class="nx">object</span> <span class="nx">nextContext</span>
|
||
<span class="p">)</span>
|
||
|
||
<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> <span class="nx">object</span> <span class="nx">nextContext</span>
|
||
<span class="p">)</span>
|
||
|
||
<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> <span class="nx">object</span> <span class="nx">prevContext</span>
|
||
<span class="p">)</span>
|
||
</code></pre></div><h2><a class="anchor" name="-context"></a>在无状态函数组件里引用 context <a class="hash-link" href="#-context">#</a></h2>
|
||
<p>无状态函数同样能够引用 <code>context</code> 如果 <code>contextTypes</code> 被定义为函数的属性.下面的代码展示了被写为无状态函数组件的 <code>Button</code> 组件.</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">function</span> <span class="nx">Button</span><span class="p">(</span><span class="nx">props</span><span class="p">,</span> <span class="nx">context</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">button</span> <span class="nx">style</span><span class="o">=</span><span class="p">{{</span><span class="nx">background</span><span class="o">:</span> <span class="nx">context</span><span class="p">.</span><span class="nx">color</span><span class="p">}}</span><span class="o">></span>
|
||
<span class="p">{</span><span class="nx">props</span><span class="p">.</span><span class="nx">children</span><span class="p">}</span>
|
||
<span class="o"><</span><span class="err">/button></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="nx">Button</span><span class="p">.</span><span class="nx">contextTypes</span> <span class="o">=</span> <span class="p">{</span><span class="nx">color</span><span class="o">:</span> <span class="nx">React</span><span class="p">.</span><span class="nx">PropTypes</span><span class="p">.</span><span class="nx">string</span><span class="p">};</span>
|
||
</code></pre></div><h2><a class="anchor" name="updating-context"></a>Updating context <a class="hash-link" href="#updating-context">#</a></h2>
|
||
<p>当 state 或者 props 变化时 <code>getChildContext</code> 函数会被调用。为了更新context里的数据，用 <code>this.setState</code> 触发一个本地的state更新。这将会触发一个新的 context 并且子级将收到变化。</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">MediaQuery</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">getInitialState</span><span class="o">:</span> <span class="kd">function</span><span class="p">(){</span>
|
||
<span class="k">return</span> <span class="p">{</span><span class="nx">type</span><span class="o">:</span><span class="s1">'desktop'</span><span class="p">};</span>
|
||
<span class="p">},</span>
|
||
<span class="nx">childContextTypes</span><span class="o">:</span> <span class="p">{</span>
|
||
<span class="nx">type</span><span class="o">:</span> <span class="nx">React</span><span class="p">.</span><span class="nx">PropTypes</span><span class="p">.</span><span class="nx">string</span>
|
||
<span class="p">},</span>
|
||
<span class="nx">getChildContext</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="nx">type</span><span class="o">:</span> <span class="k">this</span><span class="p">.</span><span class="nx">state</span><span class="p">.</span><span class="nx">type</span><span class="p">};</span>
|
||
<span class="p">},</span>
|
||
<span class="nx">componentDidMount</span><span class="o">:</span> <span class="kd">function</span><span class="p">(){</span>
|
||
<span class="kd">var</span> <span class="nx">checkMediaQuery</span> <span class="o">=</span> <span class="kd">function</span><span class="p">(){</span>
|
||
<span class="kd">var</span> <span class="nx">type</span> <span class="o">=</span> <span class="nb">window</span><span class="p">.</span><span class="nx">matchMedia</span><span class="p">(</span><span class="s2">"(min-width: 1025px)"</span><span class="p">).</span><span class="nx">matches</span> <span class="o">?</span> <span class="s1">'desktop'</span> <span class="o">:</span> <span class="s1">'mobile'</span><span class="p">;</span>
|
||
<span class="k">if</span> <span class="p">(</span><span class="nx">type</span> <span class="o">!==</span> <span class="k">this</span><span class="p">.</span><span class="nx">state</span><span class="p">.</span><span class="nx">type</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">type</span><span class="o">:</span><span class="nx">type</span><span class="p">});</span>
|
||
<span class="p">}</span>
|
||
<span class="p">};</span>
|
||
|
||
<span class="nb">window</span><span class="p">.</span><span class="nx">addEventListener</span><span class="p">(</span><span class="s1">'resize'</span><span class="p">,</span> <span class="nx">checkMediaQuery</span><span class="p">);</span>
|
||
<span class="nx">checkMediaQuery</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="k">return</span> <span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">children</span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
</code></pre></div><h2><a class="anchor" name="-context"></a>什么时候不用 context <a class="hash-link" href="#-context">#</a></h2>
|
||
<p>正像全局变量是在写清晰代码时最好要避免的,你应该在大多数情况下避免使用context. 特别是,在用它来"节省输入"和代替显示传入props时要三思.</p>
|
||
|
||
<p>context最好的使用场景是隐式的传入登录的用户,当前的语言,或者主题信息.要不然所有这些可能就是全局变量,但是context让你限定他们到一个单独的React树里.</p>
|
||
|
||
<p>不要用context在组件里传递你的模型数据.通过树显示的传递你的数据更容易理解.使用context使你的组件更耦合和不可复用,因为 依赖于他们在哪里渲染,他们会表现不同的行为.</p>
|
||
<h2><a class="anchor" name=""></a>已知的限制 <a class="hash-link" href="#">#</a></h2>
|
||
<p>如果一个由组件提供的context值变动,使用那个值的子级不会更新,如果一个直接的父级从 <code>shouldComponentUpdate</code> 返回 <code>false</code> .详见 issue <a href="https://github.com/facebook/react/issues/2517">#2517</a> . </p>
|
||
|
||
|
||
<div class="docs-prevnext">
|
||
|
||
<a class="docs-prev" href="/react/docs/advanced-performance-zh-CN.html">← Prev</a>
|
||
|
||
|
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||
</div>
|
||
</section>
|
||
|
||
|
||
<footer class="wrap">
|
||
<div class="left">
|
||
A Facebook & Instagram collaboration.<br>
|
||
<a href="/react/acknowledgements.html">Acknowledgements</a>
|
||
</div>
|
||
<div class="right">
|
||
© 2013–2016 Facebook Inc.<br>
|
||
Documentation licensed under <a href="https://creativecommons.org/licenses/by/4.0/">CC BY 4.0</a>.
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