vue狀態管理演進

概述

在vue中涉及到比較複雜的資料流轉、互動，我們一般都會考慮用vux來進行資料的狀態管理。經常使用，時常想它是怎麼實現的，嘗試簡易實現一下。

以選舉日為例，一般的元件寫法

<template>
  <div>
    <h1>Election day!</h1>
    <button @click="voteForRed">Vote for ?</button>
    <button @click="voteForBlue">Vote for ?</button>

    <h2>Results</h2>
    <results :red="red" :blue="blue" />
    <total-votes :total="red + blue" />
  </div>
</template>

<script>
const TotalVotes = {
  props: ['total'],
  render (h) {
    return h('div', `Total votes: ${this.total}`)
  }
}
const Results = {
  props: ['red', 'blue'],
  render (h) {
    return h('div', `Red: ${this.red} - Blue: ${this.blue}`)
  }
}
export default {
  components: { TotalVotes, Results, },
  data: () => ({ red: 0, blue: 0 }),
  methods: {
    voteForRed () { this.red++ },
    voteForBlue () { this.blue++ },
  }
}
</script>
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隔離狀態讓我們建立一個state物件，並從那裡管理我們的整轉態。

const state = {
  red: 0,
  blue: 0,
}

const TotalVotes = {
  render: h => h('div', `Total votes: ${state.red + state.blue}`)
}
const Results = {
  render: h => h('div', `Red: ${state.red} - Blue: ${state.blue}`),
}
// ...and, inside our main component,...
methods: {
  voteForRed () { state.red++ },
  voteForBlue () { state.blue++ },
},
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遺憾的是這不能正常工作，這是為什麼？因為Vue使用資料方法來觸發其“響應式反應”。如果不將資料傳遞給data，Vue將無法跟蹤值更改並更新我們的元件以作為響應，更新檢視。修改一下。

<template>
  <div>
    <h1>Election day!</h1>
    <button @click="voteForRed">Vote for ?</button>
    <button @click="voteForBlue">Vote for ?</button>

    <h2>Results</h2>
    <results/>
    <total-votes/>
  </div>
</template>

<script>
const state = {
  red: 0,
  blue: 0,
}
const TotalVotes = {
  data () { return state },
  render (h) {
    return h('div', `Total votes: ${this.red + this.blue}`)
  },
}
const Results = {
  data () { return state },
  render (h) {
    return h('div', `Red: ${this.red} - Blue: ${this.blue}`)
  },
}
export default {
  components: { TotalVotes, Results },
  data () { return state },
  methods: {
    voteForRed () { this.red++ },
    voteForBlue () { this.blue++ },
  },
}
</script>
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注意

元件TotalVotes、Results的props已經去除
每一個元件在state中註冊了state，Vue能夠追蹤狀態變化，因此當我們投票給所有元件時，所有元件都會以適當的值進行重新渲染
渲染函式中刪除了箭頭函式
上面的實現方式存在缺陷，每個元件都要註冊state，耦合性較高，繼續改進
建立共享Vue例項以保持響應式（資料變化觸發檢視更新）

import Vue from 'vue'
const state = new Vue({
  data () {
    return { red: 0, blue: 0 }
  },
  methods: {
    voteForRed () { this.red++ },
    voteForBlue () { this.blue++ },
  },
})
const TotalVotes = {
  render: h => h('div', `Total votes: ${state.red + state.blue}`),
}
const Results = {
  render: h => h('div', `Red: ${state.red} - Blue: ${state.blue}`),
}
export default {
  components: { TotalVotes, Results },
  methods: {
    voteForRed () { state.voteForRed() },
    voteForBlue () { state.voteForBlue() },
  },
}
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至此實現了簡單的狀態管理，但我們的解決方案目前無法在專案之間共享。我需要建立一個Vue例項，填充其資料方法，然後註冊一些方法來修改狀態，繼續封裝。

封裝

<!--模板-->
<template>
   <div>
    <h1>Election day!</h1>
    <button @click="voteForRed">Vote for ?</button>
    <button @click="voteForBlue">Vote for ?</button>

    <h2>Results</h2>
    <results :red="red" :blue="blue" />
    <total-votes :total="red + blue" />
  </div>
</template>

<!--js-->
<script>
  import Vue from 'vue'

  const createStore = ({state, mutations}) => {
    return new Vue({
      data () {
        return {state}
      },
      methods: {
        commit (mutationName) {
          mutations[mutationName](this.state)
        }
      }
    })
  }

  const store = createStore({
    state: { red: 0, blue: 0 },
    mutations: {
      voteForRed (state) { state.red++ },
      voteForBlue (state) { state.blue++ }
    }
  })

  const TotalVotes = {
    render: h => h('div', `Total votes: ${store.state.red + store.state.blue}`)
  }
  
  const Results = {
    render: h => h('div', `Red: ${store.state.red} - Blue: ${store.state.blue}`)
  }

  export default {
    components: { TotalVotes, Results },
    methods: {
      voteForRed () { store.commit('voteForRed') },
      voteForBlue () { store.commit('voteForBlue') }
    }
  }
</script>  
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vue狀態管理演進

vue狀態管理演進

概述

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