{"id":447,"date":"2021-07-05T00:04:54","date_gmt":"2021-07-04T16:04:54","guid":{"rendered":"http:\/\/zhuxinyong.com\/?p=447"},"modified":"2021-07-19T08:17:31","modified_gmt":"2021-07-19T00:17:31","slug":"%e6%b7%b1%e5%85%a5keep-alive%e7%bb%84%e4%bb%b6%e5%ae%9e%e7%8e%b0","status":"publish","type":"post","link":"https:\/\/zhuxinyong.com\/?p=447","title":{"rendered":"\u6df1\u5165keep-alive\u7ec4\u4ef6\u5b9e\u73b0"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

\u4ece\u6e90\u7801\u89d2\u5ea6\u770b\u4e00\u4e0bkeep-alive\u7ec4\u4ef6\u7a76\u7adf\u662f\u5982\u4f55\u5b9e\u73b0\u7ec4\u4ef6\u7684\u7f13\u5b58\u7684\u5462\uff1f<\/p>\n\n\n\n

created\u4e0edestroyed\u94a9\u5b50<\/h3>\n\n\n\n

created\u94a9\u5b50\u4f1a\u521b\u5efa\u4e00\u4e2acache\u5bf9\u8c61\uff0c\u7528\u6765\u4f5c\u4e3a\u7f13\u5b58\u5bb9\u5668\uff0c\u4fdd\u5b58vnode\u8282\u70b9\u3002<\/p>\n\n\n\n

created () {\n    \/* \u7f13\u5b58\u5bf9\u8c61 *\/\n    this.cache = Object.create(null)\n},\n<\/pre>\n\n\n\n
destroyed\u94a9\u5b50\u5219\u5728\u7ec4\u4ef6\u88ab\u9500\u6bc1\u7684\u65f6\u5019\u6e05\u9664cache\u7f13\u5b58\u4e2d\u7684\u6240\u6709\u7ec4\u4ef6\u5b9e\u4f8b\u3002<\/p>\n\n\n\n
\/* destroyed\u94a9\u5b50\u4e2d\u9500\u6bc1\u6240\u6709cache\u4e2d\u7684\u7ec4\u4ef6\u5b9e\u4f8b *\/\ndestroyed () {\n    for (const key in this.cache) {\n        pruneCacheEntry(this.cache[key])\n    }\n},\n<\/pre>\n\n\n\n
render<\/h3>\n\n\n\n
\u63a5\u4e0b\u6765\u662frender\u51fd\u6570\u3002<\/p>\n\n\n\n
render () {\n    \/* \u5f97\u5230slot\u63d2\u69fd\u4e2d\u7684\u7b2c\u4e00\u4e2a\u7ec4\u4ef6 *\/\n    const vnode: VNode = getFirstComponentChild(this.$slots.default)\n\n    const componentOptions: ?VNodeComponentOptions = vnode && vnode.componentOptions\n    if (componentOptions) {\n        \/\/ check pattern\n        \/* \u83b7\u53d6\u7ec4\u4ef6\u540d\u79f0\uff0c\u4f18\u5148\u83b7\u53d6\u7ec4\u4ef6\u7684name\u5b57\u6bb5\uff0c\u5426\u5219\u662f\u7ec4\u4ef6\u7684tag *\/\n        const name: ?string = getComponentName(componentOptions)\n        \/* name\u4e0d\u5728inlcude\u4e2d\u6216\u8005\u5728exlude\u4e2d\u5219\u76f4\u63a5\u8fd4\u56devnode\uff08\u6ca1\u6709\u53d6\u7f13\u5b58\uff09 *\/\n        if (name && (\n        (this.include && !matches(this.include, name)) ||\n        (this.exclude && matches(this.exclude, name))\n        )) {\n            return vnode\n        }\n        const key: ?string = vnode.key == null\n        \/\/ same constructor may get registered as different local components\n        \/\/ so cid alone is not enough (#3269)\n        ? componentOptions.Ctor.cid + (componentOptions.tag ? `::${componentOptions.tag}` : '')\n        : vnode.key\n        \/* \u5982\u679c\u5df2\u7ecf\u505a\u8fc7\u7f13\u5b58\u4e86\u5219\u76f4\u63a5\u4ece\u7f13\u5b58\u4e2d\u83b7\u53d6\u7ec4\u4ef6\u5b9e\u4f8b\u7ed9vnode\uff0c\u8fd8\u672a\u7f13\u5b58\u8fc7\u5219\u8fdb\u884c\u7f13\u5b58 *\/\n        if (this.cache[key]) {\n            vnode.componentInstance = this.cache[key].componentInstance\n        } else {\n            this.cache[key] = vnode\n        }\n        \/* keepAlive\u6807\u8bb0\u4f4d *\/\n        vnode.data.keepAlive = true\n    }\n    return vnode\n}\n<\/pre>\n\n\n\n
\u9996\u5148\u901a\u8fc7getFirstComponentChild\u83b7\u53d6\u7b2c\u4e00\u4e2a\u5b50\u7ec4\u4ef6\uff0c\u83b7\u53d6\u8be5\u7ec4\u4ef6\u7684name\uff08\u5b58\u5728\u7ec4\u4ef6\u540d\u5219\u76f4\u63a5\u4f7f\u7528\u7ec4\u4ef6\u540d\uff0c\u5426\u5219\u4f1a\u4f7f\u7528tag\uff09\u3002\u63a5\u4e0b\u6765\u4f1a\u5c06\u8fd9\u4e2aname\u901a\u8fc7include\u4e0eexclude\u5c5e\u6027\u8fdb\u884c\u5339\u914d\uff0c\u5339\u914d\u4e0d\u6210\u529f\uff08\u8bf4\u660e\u4e0d\u9700\u8981\u8fdb\u884c\u7f13\u5b58\uff09\u5219\u4e0d\u8fdb\u884c\u4efb\u4f55\u64cd\u4f5c\u76f4\u63a5\u8fd4\u56devnode\uff0cvnode\u662f\u4e00\u4e2aVNode\u7c7b\u578b\u7684\u5bf9\u8c61<\/p>\n\n\n\n
\/* \u68c0\u6d4bname\u662f\u5426\u5339\u914d *\/\nfunction matches (pattern: string | RegExp, name: string): boolean {\n  if (typeof pattern === 'string') {\n    \/* \u5b57\u7b26\u4e32\u60c5\u51b5\uff0c\u5982a,b,c *\/\n    return pattern.split(',').indexOf(name) > -1\n  } else if (isRegExp(pattern)) {\n    \/* \u6b63\u5219 *\/\n    return pattern.test(name)\n  }\n  \/* istanbul ignore next *\/\n  return false\n}\n<\/pre>\n\n\n\n
\u68c0\u6d4binclude\u4e0eexclude\u5c5e\u6027\u5339\u914d\u7684\u51fd\u6570\u5f88\u7b80\u5355\uff0cinclude\u4e0eexclude\u5c5e\u6027\u652f\u6301\u5b57\u7b26\u4e32\u5982”a,b,c”\u8fd9\u6837\u7ec4\u4ef6\u540d\u4ee5\u9017\u53f7\u9694\u5f00\u7684\u60c5\u51b5\u4ee5\u53ca\u6b63\u5219\u8868\u8fbe\u5f0f\u3002matches\u901a\u8fc7\u8fd9\u4e24\u79cd\u65b9\u5f0f\u5206\u522b\u68c0\u6d4b\u662f\u5426\u5339\u914d\u5f53\u524d\u7ec4\u4ef6\u3002<\/p>\n\n\n\n
if (this.cache[key]) {\n    vnode.componentInstance = this.cache[key].componentInstance\n} else {\n    this.cache[key] = vnode\n}\n<\/pre>\n\n\n\n
\u63a5\u4e0b\u6765\u7684\u4e8b\u60c5\u5f88\u7b80\u5355\uff0c\u6839\u636ekey\u5728this.cache\u4e2d\u67e5\u627e\uff0c\u5982\u679c\u5b58\u5728\u5219\u8bf4\u660e\u4e4b\u524d\u5df2\u7ecf\u7f13\u5b58\u8fc7\u4e86\uff0c\u76f4\u63a5\u5c06\u7f13\u5b58\u7684vnode\u7684componentInstance\uff08\u7ec4\u4ef6\u5b9e\u4f8b\uff09\u8986\u76d6\u5230\u76ee\u524d\u7684vnode\u4e0a\u9762\u3002\u5426\u5219\u5c06vnode\u5b58\u50a8\u5728cache\u4e2d\u3002<\/p>\n\n\n\n
\u6700\u540e\u8fd4\u56devnode\uff08\u6709\u7f13\u5b58\u65f6\u8be5vnode\u7684componentInstance\u5df2\u7ecf\u88ab\u66ff\u6362\u6210\u7f13\u5b58\u4e2d\u7684\u4e86\uff09\u3002<\/p>\n\n\n\n
<\/a>watch<\/h3>\n\n\n\n
\u7528watch\u6765\u76d1\u542cpruneCache\u4e0epruneCache\u8fd9\u4e24\u4e2a\u5c5e\u6027\u7684\u6539\u53d8\uff0c\u5728\u6539\u53d8\u7684\u65f6\u5019\u4fee\u6539cache\u7f13\u5b58\u4e2d\u7684\u7f13\u5b58\u6570\u636e\u3002<\/p>\n\n\n\n
watch: {\n    \/* \u76d1\u89c6include\u4ee5\u53caexclude\uff0c\u5728\u88ab\u4fee\u6539\u7684\u65f6\u5019\u5bf9cache\u8fdb\u884c\u4fee\u6b63 *\/\n    include (val: string | RegExp) {\n        pruneCache(this.cache, this._vnode, name => matches(val, name))\n    },\n    exclude (val: string | RegExp) {\n        pruneCache(this.cache, this._vnode, name => !matches(val, name))\n    }\n},\n<\/pre>\n\n\n\n
\u6765\u770b\u4e00\u4e0bpruneCache\u7684\u5b9e\u73b0\u3002<\/p>\n\n\n\n
\/* \u4fee\u6b63cache *\/\nfunction pruneCache (cache: VNodeCache, current: VNode, filter: Function) {\n  for (const key in cache) {\n    \/* \u53d6\u51facache\u4e2d\u7684vnode *\/\n    const cachedNode: ?VNode = cache[key]\n    if (cachedNode) {\n      const name: ?string = getComponentName(cachedNode.componentOptions)\n      \/* name\u4e0d\u7b26\u5408filter\u6761\u4ef6\u7684\uff0c\u540c\u65f6\u4e0d\u662f\u76ee\u524d\u6e32\u67d3\u7684vnode\u65f6\uff0c\u9500\u6bc1vnode\u5bf9\u5e94\u7684\u7ec4\u4ef6\u5b9e\u4f8b\uff08Vue\u5b9e\u4f8b\uff09\uff0c\u5e76\u4ececache\u4e2d\u79fb\u9664 *\/\n      if (name && !filter(name)) {\n        if (cachedNode !== current) {\n          pruneCacheEntry(cachedNode)\n        }\n        cache[key] = null\n      }\n    }\n  }\n} \n\n\/* \u9500\u6bc1vnode\u5bf9\u5e94\u7684\u7ec4\u4ef6\u5b9e\u4f8b\uff08Vue\u5b9e\u4f8b\uff09 *\/\nfunction pruneCacheEntry (vnode: ?VNode) {\n  if (vnode) {\n    vnode.componentInstance.$destroy()\n  }\n}\n<\/pre>\n\n\n\n
\u904d\u5386cache\u4e2d\u7684\u6240\u6709\u9879\uff0c\u5982\u679c\u4e0d\u7b26\u5408filter\u6307\u5b9a\u7684\u89c4\u5219\u7684\u8bdd\uff0c\u5219\u4f1a\u6267\u884cpruneCacheEntry\u3002pruneCacheEntry\u5219\u4f1a\u8c03\u7528\u7ec4\u4ef6\u5b9e\u4f8b\u7684$destroy\u65b9\u6cd5\u6765\u5c06\u7ec4\u4ef6\u9500\u6bc1\u3002<\/p>\n\n\n\n
<\/a><\/h2>\n\n\n\n
\u6700\u540e<\/h2>\n\n\n\n
Vue.js\u5185\u90e8\u5c06DOM\u8282\u70b9\u62bd\u8c61\u6210\u4e86\u4e00\u4e2a\u4e2a\u7684Vnode\u8282\u70b9\uff0ckeep-alive\u7ec4\u4ef6\u7684\u7f13\u5b58\u4e5f\u662f\u57fa\u4e8eVNode\u8282\u70b9\u7684\u800c\u4e0d\u662f\u76f4\u63a5\u5b58\u50a8DOM\u7ed3\u6784\u3002\u5b83\u5c06\u6ee1\u8db3\u6761\u4ef6\u7684\u7ec4\u4ef6\u5728cache\u5bf9\u8c61\u4e2d\u7f13\u5b58\u8d77\u6765\uff0c\u5728\u9700\u8981\u91cd\u65b0\u6e32\u67d3\u7684\u65f6\u5019\u518d\u5c06vnode\u8282\u70b9\u4ececache\u5bf9\u8c61\u4e2d\u53d6\u51fa\u5e76\u6e32\u67d3\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
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