Vuex学习总结

4.Vuex核心概念

4.2 Getters

Vuex实例的getters相当于计算属性，getters的结果根据其依赖关系进行缓存，并且在其依赖发生更改时才重新计算。
getters将Vuex实例的state作为第一个参数。

// store/index.js
import Vue from 'vue'
import Vuex from 'vuex'

Vue.use(Vuex)

export default new Vuex.Store({
  state: {
    todos: [
      {id: 1, text: 'study', done: true},
      {id: 2, text: 'housework', done: false},
    ],
  },
  getters: {
    doneTodos: state => {
      return state.todos.filter(todo => todo.done)
    },
    doneTodosCount: (state, getters) => {
      return getters.doneTodos.length
    },
    getTodoById: (state) => (id) => {
      return state.todos.find(todo => todo.id === id)
    },
  },
})

在组件中直接使用。

{{this.$store.getters.doneTodos[0].text}}
<br/>
{{this.$store.getters.doneTodosCount}}
<br/>
{{this.$store.getters.getTodoById(2).text}}

通过mapGetters使用。

<template>
  <div class="about">
    <h1>This is an about page</h1>
    {{$store.state.count}}
    <br/>
    {{doneTodos[0].text}}
    <br/>
    {{doneTodosCount}}
    <br/>
    {{getTodoById(2).text}}
  </div>
</template>

<script>
  import {mapGetters} from 'vuex'

  export default {
    computed: mapGetters(['doneTodos','doneTodosCount','getTodoById'])
  }
</script>