vuex-help

<!DOCTYPE HTML> <html lang="fr" > <head> <meta charset="UTF-8"> <meta content="text/html; charset=utf-8" http-equiv="Content-Type"> <title>Accesseurs · Vuex</title> <meta http-equiv="X-UA-Compatible" content="IE=edge" /> <meta name="description" content=""> <meta name="generator" content="GitBook 3.2.3"> <link rel="stylesheet" href="../gitbook/style.css"> <link rel="stylesheet" href="../gitbook/gitbook-plugin-prism/prism.css"> <link rel="stylesheet" href="../gitbook/gitbook-plugin-search/search.css"> <link rel="stylesheet" href="../gitbook/gitbook-plugin-theme-vuejs/vue.css"> <meta name="HandheldFriendly" content="true"/> <meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no"> <meta name="apple-mobile-web-app-capable" content="yes"> <meta name="apple-mobile-web-app-status-bar-style" content="black"> <link rel="apple-touch-icon-precomposed" sizes="152x152" href="../gitbook/images/apple-touch-icon-precomposed-152.png"> <link rel="shortcut icon" href="../gitbook/images/favicon.ico" type="image/x-icon"> <link rel="next" href="mutations.html" /> <link rel="prev" href="state.html" /> </head> <body> <div class="book"> <div class="book-summary"> <div id="book-search-input" role="search"> <input type="text" placeholder="Tapez pour rechercher" /> </div> <nav role="navigation"> <script async type="text/javascript" src="//cdn.carbonads.com/carbon.js?zoneid=1673&serve=C6AILKT&placement=vuejs" id="_carbonads_js"></script> <ul class="summary"> <li class="chapter " data-level="1.1" data-path="./"> <a href="./"> Introduction </a> </li> <li class="chapter " data-level="1.2" > <a target="_blank" href="https://github.com/vuejs/vuex/releases"> Notes de version </a> </li> <li class="chapter " data-level="1.3" data-path="installation.html"> <a href="installation.html"> Installation </a> </li> <li class="chapter " data-level="1.4" data-path="intro.html"> <a href="intro.html"> Vuex, qu'est-ce que c'est ? </a> </li> <li class="chapter " data-level="1.5" data-path="getting-started.html"> <a href="getting-started.html"> Pour commencer </a> </li> <li class="chapter " data-level="1.6" data-path="core-concepts.html"> <a href="core-concepts.html"> Concepts de base </a> <ul class="articles"> <li class="chapter " data-level="1.6.1" data-path="state.html"> <a href="state.html"> État </a> </li> <li class="chapter active" data-level="1.6.2" data-path="getters.html"> <a href="getters.html"> Accesseurs </a> </li> <li class="chapter " data-level="1.6.3" data-path="mutations.html"> <a href="mutations.html"> Mutations </a> </li> <li class="chapter " data-level="1.6.4" data-path="actions.html"> <a href="actions.html"> Actions </a> </li> <li class="chapter " data-level="1.6.5" data-path="modules.html"> <a href="modules.html"> Modules </a> </li> </ul> </li> <li class="chapter " data-level="1.7" data-path="structure.html"> <a href="structure.html"> Structure d'une application </a> </li> <li class="chapter " data-level="1.8" data-path="plugins.html"> <a href="plugins.html"> Plugins </a> </li> <li class="chapter " data-level="1.9" data-path="strict.html"> <a href="strict.html"> Mode strict </a> </li> <li class="chapter " data-level="1.10" data-path="forms.html"> <a href="forms.html"> Gestion des formulaires </a> </li> <li class="chapter " data-level="1.11" data-path="testing.html"> <a href="testing.html"> Tests </a> </li> <li class="chapter " data-level="1.12" data-path="hot-reload.html"> <a href="hot-reload.html"> Rechargement à chaud </a> </li> <li class="chapter " data-level="1.13" data-path="api.html"> <a href="api.html"> Documentation de l'API </a> </li> <li class="divider"></li> <li> <a href="https://www.gitbook.com" target="blank" class="gitbook-link"> Publié avec GitBook </a> </li> </ul> </nav> </div> <div class="book-body"> <div class="body-inner"> <div class="book-header" role="navigation">  <h1> <a href="." >Accesseurs</a> </h1> </div> <div class="page-wrapper" tabindex="-1" role="main"> <div class="page-inner"> <div id="book-search-results"> <div class="search-noresults"> <section class="normal markdown-section"> <h1 id="accesseurs">Accesseurs</h1> Parfois nous avons besoin de calculer des valeurs basées sur l'état du store, par exemple pour filtrer une liste d'éléments et les compter : <pre class="language-"><code class="lang-js">computed: { doneTodosCount () { return this.$store.state.todos.filter(todo => todo.done).length } } </code></pre> Si plus d'un composant a besoin d'utiliser cela, il nous faut ou bien dupliquer cette fonction, ou bien l'extraire dans une fonction utilitaire séparée et l'importer aux endroits nécessaires. Les deux idées sont loin d'être idéales. Vuex nous permet de définir des accesseurs (« getters ») dans le store. Voyez-les comme les propriétés calculées des stores. Comme pour les propriétés calculées, le résultat de l'accesseur est mis en cache en se basant sur ses dépendances et il ne sera réévalué que lorsque l'une de ses dépendances aura changée. Les accesseurs prennent l'état en premier argument : <pre class="language-"><code class="lang-js">const store = new Vuex.Store({ state: { todos: [ { id: 1, text: '...', done: true }, { id: 2, text: '...', done: false } ] }, getters: { doneTodos: state => { return state.todos.filter(todo => todo.done) } } }) </code></pre> Les accesseurs seront exposés sur l'objet <code>store.getters</code> : <pre class="language-"><code class="lang-js">store.getters.doneTodos // -> [{ id: 1, text: '...', done: true }] </code></pre> Les accesseurs recevront également les autres accesseurs en second argument : <pre class="language-"><code class="lang-js">getters: { // ... doneTodosCount: (state, getters) => { return getters.doneTodos.length } } </code></pre> <pre class="language-"><code class="lang-js">store.getters.doneTodosCount // -> 1 </code></pre> Nous pouvons maintenant facilement les utiliser dans n'importe quel composant : <pre class="language-"><code class="lang-js">computed: { doneTodosCount () { return this.$store.getters.doneTodosCount } } </code></pre> Vous pouvez aussi passer des arguments aux accesseurs en retournant une fonction. Cela est particulièrement utile quand vous souhaitez interroger un tableau dans le store : <pre class="language-"><code class="lang-js">getters: { // ... getTodoById: (state) => (id) => { return state.todos.find(todo => todo.id === id) } } </code></pre> <pre class="language-"><code class="lang-js">store.getters.getTodoById(2) // -> { id: 2, text: '...', done: false } </code></pre> <h3 id="la-fonction-utilitaire-mapgetters">La fonction utilitaire <code>mapGetters</code></h3> La fonction utilitaire <code>mapGetters</code> attache simplement vos accesseurs du store aux propriétés calculées locales : <pre class="language-"><code class="lang-js">import { mapGetters } from 'vuex' export default { // ... computed: { // rajouter les accesseurs dans `computed` avec l'opérateur de décomposition ...mapGetters([ 'doneTodosCount', 'anotherGetter', // ... ]) } } </code></pre> Si vous voulez attacher un accesseur avec un nom différent, utilisez un objet : <pre class="language-"><code class="lang-js">...mapGetters({ // attacher `this.doneCount` à `store.getters.doneTodosCount` doneCount: 'doneTodosCount' }) </code></pre> </section> </div> <div class="search-results"> <div class="has-results"> <h1 class="search-results-title"> results matching ""</h1> <ul class="search-results-list"></ul> </div> <div class="no-results"> <h1 class="search-results-title">No results matching ""</h1> </div> </div> </div> </div> </div> <script src="//m.servedby-buysellads.com/monetization.js" type="text/javascript"></script> <div class="bsa-cpc"></div> <script> (function(){ if(typeof _bsa !== 'undefined' && _bsa) { _bsa.init('default', 'CKYD62QM', 'placement:vuejsorg', { target: '.bsa-cpc', align: 'horizontal', disable_css: 'true' }); } })(); </script> </div> <a href="state.html" class="navigation navigation-prev " aria-label="Previous page: État"> </a> <a href="mutations.html" class="navigation navigation-next " aria-label="Next page: Mutations"> </a> </div> <script> var gitbook = gitbook || []; gitbook.push(function() { gitbook.page.hasChanged({"page":{"title":"Accesseurs","level":"1.6.2","depth":2,"next":{"title":"Mutations","level":"1.6.3","depth":2,"path":"mutations.md","ref":"mutations.md","articles":[]},"previous":{"title":"État","level":"1.6.1","depth":2,"path":"state.md","ref":"state.md","articles":[]},"dir":"ltr"},"config":{"plugins":["edit-link","prism","-highlight","github","-highlight","github"],"styles":{"website":"styles/website.css","pdf":"styles/pdf.css","epub":"styles/epub.css","mobi":"styles/mobi.css","ebook":"styles/ebook.css","print":"styles/print.css"},"pluginsConfig":{"prism":{},"github":{"url":"https://github.com/vuejs/vuex/"},"livereload":{},"search":{},"theme-vuejs":{},"lunr":{"maxIndexSize":1000000,"ignoreSpecialCharacters":false},"sharing":{"facebook":false,"twitter":false,"google":false,"weibo":false,"instapaper":false,"vk":false,"all":["facebook","google","twitter","weibo","instapaper"]},"edit-link":{"label":"Éditer cette page","base":"https://github.com/vuejs/vuex/tree/dev/docs"},"theme-default":{"styles":{"website":"styles/website.css","pdf":"styles/pdf.css","epub":"styles/epub.css","mobi":"styles/mobi.css","ebook":"styles/ebook.css","print":"styles/print.css"},"showLevel":false}},"theme":"default","pdf":{"pageNumbers":true,"fontSize":12,"fontFamily":"Arial","paperSize":"a4","chapterMark":"pagebreak","pageBreaksBefore":"/","margin":{"right":62,"left":62,"top":56,"bottom":56}},"structure":{"langs":"LANGS.md","readme":"README.md","glossary":"GLOSSARY.md","summary":"SUMMARY.md"},"variables":{},"title":"Vuex","language":"fr","links":{"sharing":{"facebook":false,"twitter":false}},"gitbook":"2.x.x"},"file":{"path":"getters.md","mtime":"2018-02-17T07:20:49.000Z","type":"markdown"},"gitbook":{"version":"3.2.3","time":"2018-03-02T20:43:43.208Z"},"basePath":".","book":{"language":"fr"}}); }); </script> </div> <script src="../gitbook/gitbook.js"></script> <script src="../gitbook/theme.js"></script> <script src="../gitbook/gitbook-plugin-edit-link/plugin.js"></script> <script src="../gitbook/gitbook-plugin-github/plugin.js"></script> <script src="../gitbook/gitbook-plugin-livereload/plugin.js"></script> <script src="../gitbook/gitbook-plugin-search/search-engine.js"></script> <script src="../gitbook/gitbook-plugin-search/search.js"></script> <script src="../gitbook/gitbook-plugin-lunr/lunr.min.js"></script> <script src="../gitbook/gitbook-plugin-lunr/search-lunr.js"></script> <script src="../gitbook/gitbook-plugin-sharing/buttons.js"></script> </body> </html>