This article analyzes Pinia and Vuex, and takes you to a comprehensive understanding of these two Vue state management modes

Pinia, like Vuex, is a global state manager for Vue. In fact, Pinia is Vuex5, but in order to respect the contribution of the original author, the sweet-looking name Pinia is used.

This article will compare the different implementation methods of the two in the form of Vue3, so that you can use Pinia or Vuex in your future work with ease.

Since we want to compare the implementation of the two, we must first introduce these two state managers into our Vue3 project (do not use both Vuex and Pinia in the actual project, otherwise you will be invited to drink by colleagues Tea. Let's take a look at how they are used.

Install

• Vuex

npm i vuex -S

• Pinia

npm i pinia -S

mount

Vuex

Create a new vuexStore in the src directory. In the actual project, you only need to create a store directory. Since we need two state managers, we need to separate them and create two store directories.

Create a new vuexStore/index.js

import { createStore } from 'vuex'

export default createStore({
    //全局state，类似于vue种的data
    state() {
      return {
        vuexmsg: "hello vuex",
        name: "xiaoyue",
      };
    },


    //修改state函数
    mutations: {
    },

    //提交的mutation可以包含任意异步操作
    actions: {
    },

    //类似于vue中的计算属性
    getters: {
    },

    //将store分割成模块（module）,应用较大时使用
    modules: {
    }
})

main.js import

import { createApp } from 'vue'
import App from './App.vue'
import store from '@/store'
createApp(App).use(store).mount('#app')

App.vue test

<template>
  <div></div>
</template>
<script setup>
import { useStore } from 'vuex'
let vuexStore = useStore()
console.log(vuexStore.state.vuexmsg); //hello vuex
</script>

The page prints hello vuex normally, indicating that our Vuex has been mounted successfully

Pinia

• main.js import

import { createApp } from "vue";
import App from "./App.vue";
import {createPinia} from 'pinia'
const pinia = createPinia()
createApp(App).use(pinia).mount("#app");

• Create Store

Create a new piniaStore/storeA.js under src

import { defineStore } from "pinia";

export const storeA = defineStore("storeA", {
  state: () => {
    return {
      piniaMsg: "hello pinia",
    };
  },
  getters: {},
  actions: {},
});

• App.vue use

<template>
  <div></div>
</template>
<script setup>
import { storeA } from '@/piniaStore/storeA'
let piniaStoreA = storeA()
console.log(piniaStoreA.piniaMsg); //hello pinia
</script>

From here we can see that there are no mutations and modules in pinia, pinia does not have to introduce modules in a nested (introduced through modules) way, because each store in it is a module, such as storeA, storeB... . When we use Vuex, we need to call the modification function in mutations (described below) every time we modify the value of state, because Vuex needs to track the changes of data, which makes us more cumbersome to write. And pinia no longer needs mutations, and both synchronous and asynchronous operations can be performed in actions. As for how it finally changes to the state without mutations, we will not delve into it too much here.It seems that it should be solved in the form of hooks callback (I haven't studied it, just guessing.

Modify status

From the above, we can see the value of the state at a glance. Let's see how they modify the state.

vuex

Vuex directly modifies state in components, such as App.vue

<template>
  <div>{{vuexStore.state.vuexmsg}}</div>
</template>
<script setup>
import { useStore } from 'vuex'
let vuexStore = useStore()
vuexStore.state.vuexmsg = 'hello juejin'
console.log(vuexStore.state.vuexmsg)

</script>

可以看出我们是可以直接在组件中修改state的而且还是响应式的，但是如果这样做了，vuex不能够记录每一次state的变化记录，影响我们的调试。当vuex开启严格模式的时候，直接修改state会抛出错误，所以官方建议我们开启严格模式，所有的state变更都在vuex内部进行，在mutations进行修改。例如vuexStore/index.js:

import { createStore } from "vuex";

export default createStore({
  strict: true,
  //全局state，类似于vue种的data
  state: {
    vuexmsg: "hello vuex",
  },

  //修改state函数
  mutations: {
    setVuexMsg(state, data) {
      state.vuexmsg = data;
    },
  },

  //提交的mutation可以包含任意异步操作
  actions: {},

  //类似于vue中的计算属性
  getters: {},

  //将store分割成模块（module）,应用较大时使用
  modules: {},
});

当我们需要修改vuexmsg的时候需要提交setVuexMsg方法，如App.vue

<template>
  <div>{{ vuexStore.state.vuexmsg }}</div>
</template>
<script setup>
import { useStore } from 'vuex'
let vuexStore = useStore()
vuexStore.commit('setVuexMsg', 'hello juejin')
console.log(vuexStore.state.vuexmsg) //hello juejin

</script>

或者我们可以在actions中进行提交mutations修改state:

import { createStore } from "vuex";
export default createStore({
  strict: true,
  //全局state，类似于vue种的data
  state() {
    return {
      vuexmsg: "hello vuex",
    }
  },

  //修改state函数
  mutations: {
    setVuexMsg(state, data) {
      state.vuexmsg = data;
    },
  },

  //提交的mutation可以包含任意异步操作
  actions: {
    async getState({ commit }) {
      //const result = await xxxx 假设这里进行了请求并拿到了返回值
      commit("setVuexMsg", "hello juejin");
    },
  }
});

组件中使用dispatch进行分发actions

<template>
  <div>{{ vuexStore.state.vuexmsg }}</div>
</template>
<script setup>
import { useStore } from 'vuex'
let vuexStore = useStore()
vuexStore.dispatch('getState')

</script>

一般来说，vuex中的流程是首先actions一般放异步函数，拿请求后端接口为例，当后端接口返回值的时候，actions中会提交一个mutations中的函数，然后这个函数对vuex中的状态（state）进行一个修改，组件中再渲染这个状态，从而实现整个数据流程都在vuex内部进行便于检测。直接看图，一目了然

Pinia

• 直接修改

相比于Vuex，Pinia是可以直接修改状态的，并且调试工具能够记录到每一次state的变化，如App.vue

<template>
  <div>{{ piniaStoreA.piniaMsg }}</div>
</template>
<script setup>
import { storeA } from '@/piniaStore/storeA'
let piniaStoreA = storeA()
console.log(piniaStoreA.piniaMsg); //hello pinia

piniaStoreA.piniaMsg = 'hello juejin'
console.log(piniaStoreA.piniaMsg); //hello juejin

</script>

• $patch

使用$patch方法可以修改多个state中的值,比如我们在piniaStore/storeA.js中的state增加一个name

import { defineStore } from "pinia";

export const storeA = defineStore("storeA", {
  state: () => {
    return {
      piniaMsg: "hello pinia",
      name: "xiaoyue",
    };
  },
  getters: {},
  actions: {},
});

然后我们在App.vue中进行修改这两个state

import { storeA } from '@/piniaStore/storeA'
let piniaStoreA = storeA()
console.log(piniaStoreA.name); //xiaoyue
piniaStoreA.$patch({
  piniaMsg: 'hello juejin',
  name: 'daming'
})
console.log(piniaStoreA.name);//daming

当然也是支持修改单个状态的如

piniaStoreA.$patch({
  name: 'daming'
})

$patch还可以使用函数的方式进行修改状态

import { storeA } from '@/piniaStore/storeA'
let piniaStoreA = storeA()
cartStore.$patch((state) => {
  state.name = 'daming'
  state.piniaMsg = 'hello juejin'
})

• 在actions中进行修改

不同于Vuex的是，Pinia的actions中的函数既可以是同步的，也可以是异步的，所以在actions中修改state就行Vuex在mutations修改state一样。其实这也是我比较推荐的一种修改状态的方式，就像上面说的，这样可以实现整个数据流程都在状态管理器内部，便于管理。

在piniaStore/storeA.js的actions添加一个修改name的函数

import { defineStore } from "pinia";
export const storeA = defineStore("storeA", {
  state: () => {
    return {
      piniaMsg: "hello pinia",
      name: "xiao yue",
    };
  },
  actions: {
    setName(data) {
      this.name = data;
    },
  },
});

组件App.vue中调用不需要再使用dispatch函数，直接调用store的方法即可

import { storeA } from '@/piniaStore/storeA'
let piniaStoreA = storeA()
piniaStoreA.setName('daming')

• 重置state

Pinia可以使用$reset将状态重置为初始值

import { storeA } from '@/piniaStore/storeA' 
let piniaStoreA = storeA()
piniaStoreA.$reset()

Pinia解构(storeToRefs)

当我们组件中需要用到state中多个参数时，使用解构的方式取值往往是很方便的，但是传统的ES6解构会使state失去响应式，比如组件App.vue,我们先解构取得name值，然后再去改变name值，然后看页面是否变化

<template>
  <div>{{ name }}</div>
</template>
<script setup>
import { storeA } from '@/piniaStore/storeA'
let piniaStoreA = storeA()
let { piniaMsg, name } = piniaStoreA
piniaStoreA.$patch({
  name: 'daming'
})

</script>

浏览器展示如下

我们可以发现浏览器并没有更新页面为daming

为了解决这个问题，Pinia提供了一个结构方法storeToRefs，我们将组件App.vue使用storeToRefs解构

<template>
  <div>{{ name }}</div>
</template>
<script setup>
import { storeA } from '@/piniaStore/storeA'
import { storeToRefs } from 'pinia'
let piniaStoreA = storeA()
let { piniaMsg, name } = storeToRefs(piniaStoreA)
piniaStoreA.$patch({
  name: 'daming'
})

</script>

再看下页面变化

我们发现页面已经被更新成daming了

getters

其实Vuex中的getters和Pinia中的getters用法是一致的，用于自动监听对应state的变化，从而动态计算返回值(和vue中的计算属性差不多),并且getters的值也具有缓存特性

Pinia

我们先将piniaStore/storeA.js改为

import { defineStore } from "pinia";

export const storeA = defineStore("storeA", {
  state: () => {
    return {
      count1: 1,
      count2: 2,
    };
  },
  getters: {
    sum() {
      console.log('我被调用了!')
      return this.count1 + this.count2;
    },
  },
});

然后在组件App.vue中获取sum

<template>
  <div>{{ piniaStoreA.sum }}</div>
</template>
<script setup>
import { storeA } from '@/piniaStore/storeA'
let piniaStoreA = storeA()
console.log(piniaStoreA.sum) //3

</script>

让我们来看下什么是缓存特性。首先我们在组件多次访问sum再看下控制台打印

import { storeA } from '@/piniaStore/storeA'
let piniaStoreA = storeA()
console.log(piniaStoreA.sum)
console.log(piniaStoreA.sum)
console.log(piniaStoreA.sum)
piniaStoreA.count1 = 2
console.log(piniaStoreA.sum)

从打印结果我们可以看出只有在首次使用用或者当我们改变sum所依赖的值的时候，getters中的sum才会被调用

Vuex

Vuex中的getters使用和Pinia的使用方式类似，就不再进行过多说明,写法如下vuexStore/index.js

import { createStore } from "vuex";

export default createStore({
  strict: true,
  //全局state，类似于vue种的data
  state: {
    count1: 1,
    count2: 2,
  },

  //类似于vue中的计算属性
  getters: {
    sum(state){
      return state.count1 + state.count2
    }
  }


});

modules

如果项目比较大，使用单一状态库，项目的状态库就会集中到一个大对象上，显得十分臃肿难以维护。所以Vuex就允许我们将其分割成模块（modules），每个模块都拥有自己state，mutations,actions...。而Pinia每个状态库本身就是一个模块。

Pinia

Pinia没有modules，如果想使用多个store，直接定义多个store传入不同的id即可，如：

import { defineStore } from "pinia";

export const storeA = defineStore("storeA", {...});
export const storeB = defineStore("storeB", {...});
export const storeC = defineStore("storeB", {...});

Vuex

一般来说每个module都会新建一个文件，然后再引入这个总的入口index.js中，这里为了方便就写在了一起

import { createStore } from "vuex";
const moduleA = {
  state: () => ({ 
    count:1
   }),
  mutations: {
    setCount(state, data) {
      state.count = data;
    },
  },
  actions: {
    getuser() {
      //do something
    },
  },
  getters: { ... }
}

const moduleB = {
  state: () => ({ ... }),
  mutations: { ... },
  actions: { ... }
}

export default createStore({
  strict: true,
  //全局state，类似于vue种的data
  state() {
    return {
      vuexmsg: "hello vuex",
      name: "xiaoyue",
    };
  },
  modules: {
    moduleA,
    moduleB
  },
});

使用moduleA

import { useStore } from 'vuex'
let vuexStore = useStore()
console.log(vuexStore.state.moduleA.count) //1
vuexStore.commit('setCount', 2)
console.log(vuexStore.state.moduleA.count) //2
vuexStore.dispatch('getuser')

一般我们为了防止提交一些mutation或者actions中的方法重名，modules一般会采用命名空间的方式 namespaced: true 如moduleA：

const moduleA = {
  namespaced: true,
  state: () => ({
    count: 1,
  }),
  mutations: {
    setCount(state, data) {
      state.count = data;
    },
  },
  actions: {
    getuser() {
      //do something
    },
  },
}

此时如果我们再调用setCount或者getuser

vuexStore.commit('moduleA/setCount', 2)
vuexStore.dispatch('moduleA/getuser')

写在最后

通过以上案例我们会发现Pinia比Vuex简洁许多，所以如果我们的项目是新项目的话建议使用Pinia。 当然如果我们的项目体量不是很大，我们其实没必要引入vue的状态管理库，盲目的使用反而会徒增心智负担。

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