import { isRegExp, remove } from 'shared/util' import { getFirstComponentChild } from 'core/vdom/helpers/index' type VNodeCache = { [key: string]: ?VNode }; // 获取组件名 function getComponentName (opts: ?VNodeComponentOptions): ?string { return opts && (opts.Ctor.options.name || opts.tag) } // 一个检测name是否匹配的函数 function matches (pattern: string | RegExp | Array<string>, name: string): boolean { // 数组 if (Array.isArray(pattern)) { return pattern.indexOf(name) > -1 } else if ( typeof pattern === 'string' ) { //字符串 return pattern.split( ',' ).indexOf(name) > -1 } else if (isRegExp(pattern)) { //正则 return pattern.test(name) } /* istanbul ignore next */ return false } // 修正cache function pruneCache (keepAliveInstance: any, filter: Function) { const { cache, keys, _vnode } = keepAliveInstance for (const key in cache) { // 取出cache中的vnode const cachedNode: ?VNode = cache[key] if (cachedNode) { const name: ?string = getComponentName(cachedNode.componentOptions) /* name不符合filter条件的,同时不是目前渲染的vnode时,销毁vnode对应的组件实例(Vue实例),并从cache中移除 */ if (name && !filter(name)) { pruneCacheEntry(cache, key, keys, _vnode) } } } } function pruneCacheEntry ( cache: VNodeCache, key: string, keys: Array<string>, current?: VNode ) { const cached = cache[key] if (cached && (!current || cached.tag !== current.tag)) { /* 销毁vnode对应的组件实例(Vue实例) */ cached.componentInstance.$destroy() } cache[key] = null remove(keys, key) } const patternTypes: Array<Function> = [String, RegExp, Array] export default { name: 'keep-alive' , abstract: true , props: { include: patternTypes, exclude: patternTypes, max: [String, Number] }, created () { /* 缓存对象 */ this .cache = Object.create( null ) this .keys = [] }, /* destroyed钩子中销毁所有cache中的组件实例 */ destroyed () { for (const key in this .cache) { pruneCacheEntry( this .cache, key, this .keys) } }, mounted () { /* 监视include以及exclude,在被修改的时候对cache进行修正 */ this .$watch( 'include' , val => { pruneCache( this , name => matches(val, name)) }) this .$watch( 'exclude' , val => { pruneCache( this , name => !matches(val, name)) }) }, render () { /* 得到slot插槽中的第一个组件 */ const slot = this .$slots. default const vnode: VNode = getFirstComponentChild(slot) const componentOptions: ?VNodeComponentOptions = vnode && vnode.componentOptions if (componentOptions) { // check pattern /* 获取组件名称,优先获取组件的name字段,否则是组件的tag */ const name: ?string = getComponentName(componentOptions) const { include, exclude } = this if ( // not included (include && (!name || !matches(include, name))) || // excluded (exclude && name && matches(exclude, name)) ) { return vnode } const { cache, keys } = this const key: ?string = vnode.key == null // same constructor may get registered as different local components // so cid alone is not enough (#3269) ? componentOptions.Ctor.cid + (componentOptions.tag ? `::${componentOptions.tag}` : '' ) : vnode.key /* 如果已经做过缓存了则直接从缓存中获取组件实例给vnode,还未缓存过则进行缓存 */ if (cache[key]) { vnode.componentInstance = cache[key].componentInstance // make current key freshest remove(keys, key) keys.push(key) } else { cache[key] = vnode keys.push(key) // prune oldest entry if ( this .max && keys.length > parseInt( this .max)) { pruneCacheEntry(cache, keys[0], keys, this ._vnode) } } /* keepAlive标记位 */ vnode.data.keepAlive = true } return vnode || (slot && slot[0]) } } |