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<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>State · React Native</title><meta name="viewport" content="width=device-width"/><meta name="generator" content="Docusaurus"/><meta name="description" content="There are two types of data that control a component: `props` and `state`. `props` are set by the parent and they are fixed throughout the lifetime of a component. For data that is going to change, we have to use `state`."/><meta name="docsearch:version" content="0.50"/><meta name="docsearch:language" content="en"/><meta property="og:title" content="State · React Native"/><meta property="og:type" content="website"/><meta property="og:url" content="https://reactnative.dev/"/><meta property="og:description" content="There are two types of data that control a component: `props` and `state`. `props` are set by the parent and they are fixed throughout the lifetime of a component. For data that is going to change, we have to use `state`."/><meta property="og:image" content="https://reactnative.dev/img/logo-og.png"/><meta name="twitter:card" content="summary"/><meta name="twitter:image" content="https://reactnative.dev/img/logo-og.png"/><link rel="shortcut icon" href="/img/favicon.ico"/><link rel="stylesheet" href="https://cdn.jsdelivr.net/docsearch.js/1/docsearch.min.css"/><link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.12.0/styles/solarized-dark.min.css"/><link rel="alternate" type="application/atom+xml" href="https://reactnative.dev/blog/atom.xml" title="React Native Blog ATOM Feed"/><link rel="alternate" type="application/rss+xml" href="https://reactnative.dev/blog/feed.xml" title="React Native Blog RSS Feed"/><script>
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</script><script src="/js/scrollSpy.js"></script><link rel="stylesheet" href="/css/prism.css"/><link rel="stylesheet" href="/css/main.css"/><script src="/js/codetabs.js"></script></head><body class="sideNavVisible separateOnPageNav"><div class="fixedHeaderContainer"><div class="headerWrapper wrapper"><header><a href="/"><img class="logo" src="/img/header_logo.svg" alt="React Native"/><h2 class="headerTitleWithLogo">React Native</h2></a><a href="/versions"><h3>0.50</h3></a><div class="navigationWrapper navigationSlider"><nav class="slidingNav"><ul class="nav-site nav-site-internal"><li class="siteNavGroupActive"><a href="/docs/0.50/getting-started" target="_self">Docs</a></li><li class="siteNavGroupActive"><a href="/docs/0.50/components-and-apis" target="_self">Components</a></li><li class="siteNavGroupActive"><a href="/docs/0.50/accessibilityinfo" target="_self">API</a></li><li class=""><a href="/help" target="_self">Community</a></li><li class=""><a href="/blog/" 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</script></nav></div><div class="container mainContainer docsContainer"><div class="wrapper"><div class="post"><header class="postHeader"><a class="edit-page-link button" href="https://github.com/facebook/react-native-website/blob/master/docs/state.md" target="_blank" rel="noreferrer noopener">Edit</a><h1 id="__docusaurus" class="postHeaderTitle">State</h1></header><article><div><span><p>There are two types of data that control a component: <code>props</code> and <code>state</code>. <code>props</code> are set by the parent and they are fixed throughout the lifetime of a component. For data that is going to change, we have to use <code>state</code>.</p>
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<p>In general, you should initialize <code>state</code> in the constructor, and then call <code>setState</code> when you want to change it.</p>
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<p>For example, let's say we want to make text that blinks all the time. The text itself gets set once when the blinking component gets created, so the text itself is a <code>prop</code>. The "whether the text is currently on or off" changes over time, so that should be kept in <code>state</code>.</p>
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<div class="snack-player"><div class="mobile-friendly-snack" style="display: none"><pre><code class="hljs css javascript"><span class="hljs-keyword">import</span> React, { Component } <span class="hljs-keyword">from</span> <span class="hljs-string">'react'</span>;
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<span class="hljs-keyword">import</span> { Text, View } <span class="hljs-keyword">from</span> <span class="hljs-string">'react-native'</span>;
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<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Blink</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Component</span> </span>{
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componentDidMount(){
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<span class="hljs-comment">// Toggle the state every second</span>
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<span class="hljs-built_in">setInterval</span>(<span class="hljs-function">() =></span> (
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<span class="hljs-built_in">this</span>.setState(<span class="hljs-function"><span class="hljs-params">previousState</span> =></span> (
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{ <span class="hljs-attr">isShowingText</span>: !previousState.isShowingText }
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))
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||
), <span class="hljs-number">1000</span>);
|
||
}
|
||
|
||
<span class="hljs-comment">//state object</span>
|
||
state = { <span class="hljs-attr">isShowingText</span>: <span class="hljs-literal">true</span> };
|
||
|
||
render() {
|
||
<span class="hljs-keyword">if</span> (!<span class="hljs-built_in">this</span>.state.isShowingText) {
|
||
<span class="hljs-keyword">return</span> <span class="hljs-literal">null</span>;
|
||
}
|
||
|
||
<span class="hljs-keyword">return</span> (
|
||
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">Text</span>></span>{this.props.text}<span class="hljs-tag"></<span class="hljs-name">Text</span>></span></span>
|
||
);
|
||
}
|
||
}
|
||
|
||
<span class="hljs-keyword">export</span> <span class="hljs-keyword">default</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">BlinkApp</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Component</span> </span>{
|
||
render() {
|
||
<span class="hljs-keyword">return</span> (
|
||
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">View</span>></span>
|
||
<span class="hljs-tag"><<span class="hljs-name">Blink</span> <span class="hljs-attr">text</span>=<span class="hljs-string">'I love to blink'</span> /></span>
|
||
<span class="hljs-tag"><<span class="hljs-name">Blink</span> <span class="hljs-attr">text</span>=<span class="hljs-string">'Yes blinking is so great'</span> /></span>
|
||
<span class="hljs-tag"><<span class="hljs-name">Blink</span> <span class="hljs-attr">text</span>=<span class="hljs-string">'Why did they ever take this out of HTML'</span> /></span>
|
||
<span class="hljs-tag"><<span class="hljs-name">Blink</span> <span class="hljs-attr">text</span>=<span class="hljs-string">'Look at me look at me look at me'</span> /></span>
|
||
<span class="hljs-tag"></<span class="hljs-name">View</span>></span></span>
|
||
);
|
||
}
|
||
}
|
||
</code></pre></div><div class="desktop-friendly-snack" style="margin-top: 15px; margin-bottom: 15px"><div
|
||
data-snack-name="State"
|
||
data-snack-description="Example usage"
|
||
data-snack-code="import%20React%2C%20%7B%20Component%20%7D%20from%20'react'%3B%0Aimport%20%7B%20Text%2C%20View%20%7D%20from%20'react-native'%3B%0A%0Aclass%20Blink%20extends%20Component%20%7B%0A%0A%20%20componentDidMount()%7B%0A%20%20%20%20%2F%2F%20Toggle%20the%20state%20every%20second%0A%20%20%20%20setInterval(()%20%3D%3E%20(%0A%20%20%20%20%20%20this.setState(previousState%20%3D%3E%20(%0A%20%20%20%20%20%20%20%20%7B%20isShowingText%3A%20!previousState.isShowingText%20%7D%0A%20%20%20%20%20%20))%0A%20%20%20%20)%2C%201000)%3B%0A%20%20%7D%0A%0A%20%20%2F%2Fstate%20object%0A%20%20state%20%3D%20%7B%20isShowingText%3A%20true%20%7D%3B%0A%0A%20%20render()%20%7B%0A%20%20%20%20if%20(!this.state.isShowingText)%20%7B%0A%20%20%20%20%20%20return%20null%3B%0A%20%20%20%20%7D%0A%0A%20%20%20%20return%20(%0A%20%20%20%20%20%20%3CText%3E%7Bthis.props.text%7D%3C%2FText%3E%0A%20%20%20%20)%3B%0A%20%20%7D%0A%7D%0A%0Aexport%20default%20class%20BlinkApp%20extends%20Component%20%7B%0A%20%20render()%20%7B%0A%20%20%20%20return%20(%0A%20%20%20%20%20%20%3CView%3E%0A%20%20%20%20%20%20%20%20%3CBlink%20text%3D'I%20love%20to%20blink'%20%2F%3E%0A%20%20%20%20%20%20%20%20%3CBlink%20text%3D'Yes%20blinking%20is%20so%20great'%20%2F%3E%0A%20%20%20%20%20%20%20%20%3CBlink%20text%3D'Why%20did%20they%20ever%20take%20this%20out%20of%20HTML'%20%2F%3E%0A%20%20%20%20%20%20%20%20%3CBlink%20text%3D'Look%20at%20me%20look%20at%20me%20look%20at%20me'%20%2F%3E%0A%20%20%20%20%20%20%3C%2FView%3E%0A%20%20%20%20)%3B%0A%20%20%7D%0A%7D%0A"
|
||
data-snack-platform="web"
|
||
data-snack-supported-platforms=ios,android,web
|
||
data-snack-preview="true"
|
||
style="
|
||
overflow: hidden;
|
||
background: #fafafa;
|
||
border: 1px solid rgba(0,0,0,.16);
|
||
border-radius: 4px;
|
||
height: 514px;
|
||
width: 100%;
|
||
"
|
||
></div></div></div><p>In a real application, you probably won't be setting state with a timer. You might set state when you have new data from the server, or from user input. You can also use a state container like <a href="https://redux.js.org/">Redux</a> or <a href="https://mobx.js.org/">Mobx</a> to control your data flow. In that case you would use Redux or Mobx to modify your state rather than calling <code>setState</code> directly.</p>
|
||
<p>When setState is called, BlinkApp will re-render its Component. By calling setState within the Timer, the component will re-render every time the Timer ticks.</p>
|
||
<p>State works the same way as it does in React, so for more details on handling state, you can look at the <a href="https://reactjs.org/docs/react-component.html#setstate">React.Component API</a>. At this point, you might be annoyed that most of our examples so far use the default text color. To customize the text color, you will have to <a href="/docs/0.50/style">learn about Style</a>.</p>
|
||
</span></div></article></div><div class="docs-prevnext"><a class="docs-prev button" href="/docs/0.50/props"><span class="arrow-prev">← </span><span>Props</span></a><a class="docs-next button" href="/docs/0.50/style"><span>Style</span><span class="arrow-next"> →</span></a></div></div></div><nav class="onPageNav"></nav></div><footer class="nav-footer" id="footer"><section class="sitemap"><div><h5>Docs</h5><a href="/docs/getting-started">Getting Started</a><a href="/docs/tutorial">Tutorial</a><a href="/docs/components-and-apis">Components and APIs</a><a href="/docs/more-resources">More Resources</a></div><div><h5>Community</h5><a href="/help">The React Native Community</a><a href="/showcase">Who's using React Native?</a><a href="https://stackoverflow.com/questions/tagged/react-native" target="_blank">Ask Questions on Stack Overflow</a><a href="https://github.com/facebook/react-native/blob/master/CONTRIBUTING.md">Contributor Guide</a><a href="https://dev.to/t/reactnative" target="_blank">DEV Community</a></div><div><h5>More Resources</h5><a href="/blog">Blog</a><a href="https://twitter.com/reactnative" target="_blank">Twitter</a><a href="https://github.com/facebook/react-native" target="_blank">GitHub</a><a href="https://reactjs.org" target="_blank">React</a></div></section><a href="https://code.facebook.com/projects/" target="_blank" class="fbOpenSource"><img src="/img/oss_logo.png" alt="Facebook Open Source" width="170" height="45"/></a><section class="copyright">Copyright © 2020 Facebook Inc.</section></footer></div><script type="text/javascript" src="https://cdn.jsdelivr.net/docsearch.js/1/docsearch.min.js"></script><script>window.fbAsyncInit = function() {FB.init({appId:'1677033832619985',xfbml:true,version:'v2.7'});};(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/sdk.js';fjs.parentNode.insertBefore(js, fjs);}(document, 'script','facebook-jssdk'));
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