keep-alive-2

events.js

import Vue from 'vue'

const eventBus = new Vue();

export default eventBus;

index.js

import { getComponentName, getFirstComponentChild, isArray, isRegExp, remove } from './util'
import keepAlive2Events from './events'

function _getComponentName(opts) {
  return opts && (getComponentName(opts.Ctor.options) || opts.tag)
}

function matches(
  pattern,
  name
) {
  if (isArray(pattern)) {
    return pattern.indexOf(name) > -1
  } else if (typeof pattern === 'string') {
    return pattern.split(',').indexOf(name) > -1
  } else if (isRegExp(pattern)) {
    return pattern.test(name)
  }
  /* istanbul ignore next */
  return false
}

function pruneCache(
  keepAliveInstance,
  filter
) {
  const { cache, keys, _vnode } = keepAliveInstance
  for (const key in cache) {
    const entry = cache[key]
    if (entry) {
      const name = entry.name
      if (name && !filter(name)) {
        pruneCacheEntry(cache, key, keys, _vnode)
      }
    }
  }
}

function pruneCacheEntry(
  cache,
  key,
  keys,
  current
) {
  const entry = cache[key]
  if (entry && (!current || entry.tag !== current.tag)) {
    entry.componentInstance.$destroy()
  }
  cache[key] = null
  remove(keys, key)
}

const patternTypes = [String, RegExp, Array]

export default {
  name: 'keep-alive-2',
  abstract: true,

  props: {
    include: patternTypes,
    exclude: patternTypes,
    max: [String, Number]
  },

  methods: {
    cacheVNode() {
      const { cache, keys, vnodeToCache, keyToCache } = this

      // console.log('dbg keep-alive-2 cacheVNode keyToCache', keyToCache)

      if (vnodeToCache) {
        const { tag, componentInstance, componentOptions } = vnodeToCache
        cache[keyToCache] = {
          name: _getComponentName(componentOptions),
          tag,
          componentInstance
        }
        keys.push(keyToCache)
        // prune oldest entry
        if (this.max && keys.length > parseInt(this.max)) {
          pruneCacheEntry(cache, keys[0], keys, this._vnode)
        }
        this.vnodeToCache = null
      }
    },

    onRemove(vnode) {
      const componentOptions = vnode && vnode.componentOptions
      const keyToRemove =
        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;
      
      const { cache, keys } = this
      pruneCacheEntry(cache, keyToRemove, keys, this._vnode)
    }
  },

  created() {
    this.cache = Object.create(null)
    this.keys = []

    keepAlive2Events.$on('remove', this.onRemove);
  },

  destroyed() {
    for (const key in this.cache) {
      pruneCacheEntry(this.cache, key, this.keys)
    }

    keepAlive2Events.$off('remove', this.onRemove);
  },

  mounted() {
    this.cacheVNode()
    this.$watch('include', val => {
      pruneCache(this, name => matches(val, name))
    })
    this.$watch('exclude', val => {
      pruneCache(this, name => !matches(val, name))
    })
  },

  updated() {
    this.cacheVNode()
  },

  render() {
    const slot = this.$slots.default
    const vnode = getFirstComponentChild(slot)
    const componentOptions = vnode && vnode.componentOptions
    if (componentOptions) {
      // check pattern
      const name = _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 =
        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
      if (cache[key]) {
        vnode.componentInstance = cache[key].componentInstance
        // make current key freshest
        remove(keys, key)
        keys.push(key)
      } else {
        // delay setting the cache until update
        this.vnodeToCache = vnode
        this.keyToCache = key
      }

      // @ts-expect-error can vnode.data can be undefined
      vnode.data.keepAlive = true
    }
    return vnode || (slot && slot[0])
  }
}

util.js

export const isArray = Array.isArray

export function isDef(v) {
  return v !== undefined && v !== null
}

export function isRegExp(v) {
  return _toString.call(v) === '[object RegExp]'
}

export function isAsyncPlaceholder(node) {
  return node.isComment && node.asyncFactory
}

export function remove(arr, item) {
  const len = arr.length
  if (len) {
    // fast path for the only / last item
    if (item === arr[len - 1]) {
      arr.length = len - 1
      return
    }
    const index = arr.indexOf(item)
    if (index > -1) {
      return arr.splice(index, 1)
    }
  }
}

export function getComponentName(options) {
  return options.name || options.__name || options._componentTag
}

export function getFirstComponentChild(children) {
  if (isArray(children)) {
    for (let i = 0; i < children.length; i++) {
      const c = children[i]
      if (isDef(c) && (isDef(c.componentOptions) || isAsyncPlaceholder(c))) {
        return c
      }
    }
  }
}