Vuex之理解Getters的用法实例

const getters = {style:state => state.style}

computed: {
doneTodosCount () {
  return this.$store.getters.doneTodosCount}

import { mapGetters } from 'vuex'
computed: {
  // 使用对象展开运算符将 getters 混入 computed 对象中
  ...mapGetters([
  'doneTodosCount',
  'anotherGetter',])}
 //给getter属性换名字
 mapGetters({
 // 映射 this.doneCount 为 store.getters.doneTodosCount
 doneCount: 'doneTodosCount'
})

  function `wrapGetters` (store, moduleGetters, modulePath) {
   Object.keys(moduleGetters).forEach(getterKey => {
      // 遍历先所有的getters
    const rawGetter = moduleGetters[getterKey]
    if (store._wrappedGetters[getterKey]) {
     console.error(`[vuex] duplicate getter key: ${getterKey}`)
      // getter的key不允许重复，否则会报错
     return
    }
    store._wrappedGetters[getterKey] = function `wrappedGetter` (store{
      // 将每一个getter包装成一个方法，并且添加到store._wrappedGetters对象中，
      return rawGetter(
       //执行getter的回调函数，传入三个参数，(local state,store getters,rootState)
      getNestedState(store.state, modulePath), // local state
       //根据path查找state上嵌套的state 
      store.getters, 
        // store上所有的getters
      store.state 
         // root state)}}) 
   }
   
   //根据path查找state上嵌套的state 
  function `getNestedState` (state, path) {
     return path.length
      ? path.reduce((state, key) => state[key], state): state}