vuex : 模块化改造

我们知道，vuex是vue技术栈中很重要的一部分，是一个很好用的状态管理库。

如果你的项目没有那么复杂，或者对vuex的使用没有那么重度，那么，是用不着modules功能的。

但如果你写着写着就发现你的vuex 代码过于臃肿，那么就可能需要modules功能来进行模块化改造了。

由于使用单一状态树，应用的所有状态会集中到一个比较大的对象。当应用变得非常复杂时，store 对象就有可能变得相当臃肿。

为了解决以上问题，Vuex 允许我们将 store 分割成模块（module）。每个模块拥有自己的 state、mutation、action、getter、甚至是嵌套子模块——从上至下进行同样方式的分割：

——vuex文档

那么，怎么改呢？

以文档的计数器demo为例：

这是demo的vuex代码：

import Vue from 'vue'
import Vuex from 'vuex'

Vue.use(Vuex)

// root state object.
// each Vuex instance is just a single state tree.
const state = {
  count: 0
}

// mutations are operations that actually mutates the state.
// each mutation handler gets the entire state tree as the
// first argument, followed by additional payload arguments.
// mutations must be synchronous and can be recorded by plugins
// for debugging purposes.
const mutations = {
  increment (state) {
    state.count++
  },
  decrement (state) {
    state.count--
  }
}

// actions are functions that cause side effects and can involve
// asynchronous operations.
const actions = {
  increment: ({ commit }) => commit('increment'),
  decrement: ({ commit }) => commit('decrement'),
  incrementIfOdd ({ commit, state }) {
    if ((state.count + 1) % 2 === 0) {
      commit('increment')
    }
  },
  incrementAsync ({ commit }) {
    return new Promise((resolve, reject) => {
      setTimeout(() => {
        commit('increment')
        resolve()
      }, 1000)
    })
  }
}

// getters are functions
const getters = {
  evenOrOdd: state => state.count % 2 === 0 ? 'even' : 'odd',
  originNumber: state => state.count
}

// A Vuex instance is created by combining the state, mutations, actions,
// and getters.
export default new Vuex.Store({
  state,
  getters,
  actions,
  mutations
})

1 新建文件，叫part_a.js

2 store.js的代码复制进去，并修改：

// import Vue from 'vue'
// import Vuex from 'vuex'

// Vue.use(Vuex)

// root state object.
// each Vuex instance is just a single state tree.
const state = {
  count: 0
}

// mutations are operations that actually mutates the state.
// each mutation handler gets the entire state tree as the
// first argument, followed by additional payload arguments.
// mutations must be synchronous and can be recorded by plugins
// for debugging purposes.
const mutations = {
  increment (state) {
    state.count++
  },
  decrement (state) {
    state.count--
  }
}

// actions are functions that cause side effects and can involve
// asynchronous operations.
const actions = {
  increment: ({ commit }) => commit('increment'),
  decrement: ({ commit }) => commit('decrement'),
  incrementIfOdd ({ commit, state }) {
    if ((state.count + 1) % 2 === 0) {
      commit('increment')
    }
  },
  incrementAsync ({ commit }) {
    return new Promise((resolve, reject) => {
      setTimeout(() => {
        commit('increment')
        resolve()
      }, 1000)
    })
  }
}

// getters are functions
const getters = {
  evenOrOdd: state => state.count % 2 === 0 ? 'even' : 'odd',
  originNumber: state => state.count
}

// A Vuex instance is created by combining the state, mutations, actions,
// and getters.
export default {
  namespaced: true,
  state,
  getters,
  actions,
  mutations
}

注意白底的部分：import 和 use 被注释了，输出变成了 export default { }，输出对象中加上了 namespaced: true

3 修改store.js

import Vue from 'vue'
import Vuex from 'vuex'
import part_a from './part_a'

Vue.use(Vuex)

export default new Vuex.Store({
  modules: {
    part_a    
  }
})

因为业务逻辑代码放进了part_a.js，所以store.js就不需要保留这一部分。

注意白底的部分：加上了part_a.js的引用，Store()中的对象只有modules对象，里面是引用的part_a。

4 修改*.vue文件

...
computed: {
    ...mapGetters([
      'evenOrOdd',
      'originNumber'
    ]),
  },
  methods: {
    ...mapActions([
      'increment',
      'decrement',
      'incrementIfOdd',
      'incrementAsync'
    ])
  },
...

...
computed: {
    ...mapGetters('part_a', [
      'evenOrOdd',
      'originNumber'
    ]),
  },
  methods: {
    ...mapActions('part_a', [
      'increment',
      'decrement',
      'incrementIfOdd',
      'incrementAsync'
    ])
  },
...

注意白底的部分。加一个参数就可以了。

mutations 和 state 可以只有私有调用，所以mapMutations和mapState就不需要了。

以上。