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# 36｜数据流原理：Vuex & Pinia源码剖析
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你好，我是大圣。
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上一讲我们分析了Vite原理，今天我们来剖析Vuex的原理。其实在之前的课程中，我们已经实现过一个迷你的Vuex，整体代码逻辑比较简单，基于Vue提供的响应式函数reactive和computed的能力，我们封装了一个独立的共享数据的store，并且对外暴露了commit和dispatch方法修改和更新数据，这些原理就不赘述了。
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今天我们探讨一下下一代Vuex5的提案，并且看一下实际的代码是如何实现的，你学完之后可以对比之前gvuex mini版本，感受一下两者的区别。
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## Vuex5提案
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由于Vuex有模块化namespace的功能，所以模块user中的mutation add方法，我们需要使用 `commit('user/add')` 来触发。这样虽然可以让Vuex支持更复杂的项目，但是**这种字符串类型的拼接功能，在TypeScript4之前的类型推导中就很难实现**。然后就有了Vuex5相关提案的讨论，整个讨论过程都是在GitHub的issue里推进的，你可以访问[GitHub链接](https://github.com/vuejs/rfcs/pull/271)去围观。
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Vuex5的提案相比Vuex4有很大的改进，解决了一些Vuex4中的缺点。Vuex5能够同时支持Composition API和Option API，并且去掉了namespace模式，使用组合store的方式更好地支持了TypeScript的类型推导，还去掉了容易混淆的Mutation和Action概念，只保留了Action，并且**支持自动的代码分割**。
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我们也可以通过对这个提案的研究，来体验一下在一个框架中如何讨论新的语法设计和实现，以及如何通过API的设计去解决开发方式的痛点。你可以在Github的提案RFCs中看到[Vuex5的设计文稿](https://github.com/vuejs/rfcs/blob/34a8b0d541a361a37d05de8d67cb44a7b6f6fd12/active-rfcs/0000-vuex-5.md)，而Pinia正是基于Vuex5设计的框架。
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现在Pinia已经正式合并到Vue组织下，成为了Vue的官方项目，尤雨溪也在多次分享中表示**Pinia就是未来的Vuex**，接下来我们就好好学习一下Pinia的使用方式和实现的原理。
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## Pinia
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下图是Pinia官网的介绍，可以看到类型安全、Vue 的Devtools支持、易扩展、只有1KB的体积等优点。快来看下Pinia如何使用吧。
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首先我们在项目根目录下执行下面的命令去**安装Pinia的最新版本**。
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```javascript
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npm install pinia@next
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```
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然后在src/main.js中，我们导入createPinia方法，通过createPinia方法创建Pinia的实例后，再通过app.use方法注册Pinia。
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```javascript
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import { createApp } from 'vue'
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import { createPinia } from 'pinia'
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import App from './App.vue'
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const pinia = createPinia()
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const app = createApp(App)
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app.use(pinia).mount('#app')
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```
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然后我们可以在store文件夹中创建一个count.js。下面的代码中我们通过Pinia的defineStore方法定义了一个store，store内部通过state返回一个对象，并且通过Actions配置修改数据的方法add。这里使用的语法和Vuex比较类似，只是删除了Mutation的概念，**统一使用Actions来配置**。
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```javascript
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import { defineStore } from 'pinia'
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export const useCounterStore = defineStore('count', {
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id:'count',
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state: () => {
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return { count: 1 }
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},
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actions: {
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add() {
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this.count++
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},
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},
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})
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```
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然后我们可以使用Composition的方式在代码中使用store。注意上面的store返回的其实就是一个Composition风格的函数，使用useCounterStore返回count后，可以在add方法中直接使用count.add触发Actions，实现数据的修改。
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```javascript
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import { useCounterStore } from '../stores/count'
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const count = useCounterStore()
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function add(){
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count.add()
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}
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```
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**我们也可以使用Composition风格的语法，去创建一个store。**使用ref或者reactive包裹后，通过defineStore返回，这样store就非常接近我们自己分装的Composition语法了，也去除了很多Vuex中特有的概念，学习起来更加简单。
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```javascript
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export const useCounterStore = defineStore('count', () => {
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const count = ref(0)
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function increment() {
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count.value++
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}
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return { count, increment }
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})
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```
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## Pinna源码
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然后我们通过阅读Pinia的源码，来看下Pinia是如何实现的。
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首先我们进入到Pinia的GitHub中，我们可以在packages/pinia/src/createPinia.ts中看到createPinia函数的实现。
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下面的代码中，我们通过effectScope创建一个作用域对象，并且通过ref创建了响应式的数据对象state。然后通过install方法支持了app.use的注册，内部通过provide的语法和全局的$pinia变量配置Pinia对象，并且通过use方法和toBeInstalled数组实现了Pinia的插件机制。**最后还通过pinia.use(devtoolsPlugin) 实现了对VueDevtools的支持。**
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```javascript
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export function createPinia(): Pinia {
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const scope = effectScope(true)
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// NOTE: here we could check the window object for a state and directly set it
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// if there is anything like it with Vue 3 SSR
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const state = scope.run(() => ref<Record<string, StateTree>>({}))!
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let _p: Pinia['_p'] = []
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// plugins added before calling app.use(pinia)
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let toBeInstalled: PiniaPlugin[] = []
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const pinia: Pinia = markRaw({
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install(app: App) {
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// this allows calling useStore() outside of a component setup after
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// installing pinia's plugin
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setActivePinia(pinia)
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if (!isVue2) {
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pinia._a = app
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app.provide(piniaSymbol, pinia)
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app.config.globalProperties.$pinia = pinia
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toBeInstalled.forEach((plugin) => _p.push(plugin))
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toBeInstalled = []
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}
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},
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use(plugin) {
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if (!this._a && !isVue2) {
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toBeInstalled.push(plugin)
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} else {
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_p.push(plugin)
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}
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return this
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},
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_p,
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_a: null,
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_e: scope,
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_s: new Map<string, StoreGeneric>(),
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state,
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})
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if (__DEV__ && IS_CLIENT) {
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pinia.use(devtoolsPlugin)
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}
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return pinia
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}
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```
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通过上面的代码，我们可以看到Pinia实例就是 ref({}) 包裹的响应式对象，项目中用到的state都会挂载到Pinia这个响应式对象内部。
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然后我们去看下创建store的defineStore方法, defineStore内部通过useStore方法去定义store，并且每个store都会标记唯一的ID。
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首先通过getCurrentInstance获取当前组件的实例，如果useStore参数没有Pinia的话，就使用inject去获取Pinia实例，**这里inject的数据就是createPinia函数中install方法提供的**。
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然后设置activePinia，项目中可能会存在很多Pinia的实例，设置activePinia就是设置当前活跃的Pinia实例。这个函数的实现方式和Vue中的componentInstance很像，每次创建组件的时候都设置当前的组件实例，这样就可以在组件的内部通过getCurrentInstance获取，最后通过createSetupStore或者createOptionsStore创建组件。
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这就是上面代码中我们使用Composition和Option两种语法创建store的不同执行逻辑，最后通过pinia.\_s缓存创建后的store，\_s就是在createPinia的时候创建的一个Map对象，防止store多次重复创建。**到这store创建流程就结束了。**
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```javascript
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export function defineStore(
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// TODO: add proper types from above
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idOrOptions: any,
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setup?: any,
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setupOptions?: any
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): StoreDefinition {
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let id: string
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let options:...
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const isSetupStore = typeof setup === 'function'
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if (typeof idOrOptions === 'string') {
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id = idOrOptions
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// the option store setup will contain the actual options in this case
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options = isSetupStore ? setupOptions : setup
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} else {
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options = idOrOptions
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id = idOrOptions.id
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}
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function useStore(pinia?: Pinia | null, hot?: StoreGeneric): StoreGeneric {
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const currentInstance = getCurrentInstance()
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pinia =
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// in test mode, ignore the argument provided as we can always retrieve a
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// pinia instance with getActivePinia()
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(__TEST__ && activePinia && activePinia._testing ? null : pinia) ||
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(currentInstance && inject(piniaSymbol))
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if (pinia) setActivePinia(pinia)
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pinia = activePinia!
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if (!pinia._s.has(id)) {
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// creating the store registers it in `pinia._s`
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if (isSetupStore) {
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createSetupStore(id, setup, options, pinia)
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} else {
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createOptionsStore(id, options as any, pinia)
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}
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/* istanbul ignore else */
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if (__DEV__) {
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// @ts-expect-error: not the right inferred type
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useStore._pinia = pinia
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}
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}
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const store: StoreGeneric = pinia._s.get(id)!
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// save stores in instances to access them devtools
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if (
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__DEV__ &&
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IS_CLIENT &&
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currentInstance &&
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currentInstance.proxy &&
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// avoid adding stores that are just built for hot module replacement
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!hot
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) {
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const vm = currentInstance.proxy
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const cache = '_pStores' in vm ? vm._pStores! : (vm._pStores = {})
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cache[id] = store
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}
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// StoreGeneric cannot be casted towards Store
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return store as any
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}
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useStore.$id = id
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return useStore
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}
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```
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在Pinia中createOptionsStore内部也是调用了createSetupStore来创建store对象。下面的代码中，我们通过assign方法实现了setup函数，这里可以看到computed的实现，内部就是通过pinia.\_s缓存获取store对象，调用store的getters方法来模拟，最后依然通过createSetupStore创建。
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|
|
|
|
|
```javascript
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|
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function createOptionsStore<
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Id extends string,
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S extends StateTree,
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G extends _GettersTree<S>,
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|
|
A extends _ActionsTree
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|
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|
>(
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|
|
id: Id,
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|
|
options: DefineStoreOptions<Id, S, G, A>,
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|
|
pinia: Pinia,
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|
hot?: boolean
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|
|
): Store<Id, S, G, A> {
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|
const { state, actions, getters } = options
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|
const initialState: StateTree | undefined = pinia.state.value[id]
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let store: Store<Id, S, G, A>
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function setup() {
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|
pinia.state.value[id] = state ? state() : {}
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|
return assign(
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|
localState,
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actions,
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|
|
Object.keys(getters || {}).reduce((computedGetters, name) => {
|
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|
|
|
|
computedGetters[name] = markRaw(
|
|
|
|
|
|
computed(() => {
|
|
|
|
|
|
setActivePinia(pinia)
|
|
|
|
|
|
// it was created just before
|
|
|
|
|
|
const store = pinia._s.get(id)!
|
|
|
|
|
|
return getters![name].call(store, store)
|
|
|
|
|
|
})
|
|
|
|
|
|
)
|
|
|
|
|
|
return computedGetters
|
|
|
|
|
|
}, {} as Record<string, ComputedRef>)
|
|
|
|
|
|
)
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
store = createSetupStore(id, setup, options, pinia, hot)
|
|
|
|
|
|
|
|
|
|
|
|
return store as any
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
|
|
最后我们来看一下createSetupStore函数的实现。这个函数也是Pinia中最复杂的函数实现，内部的$patch函数可以实现数据的更新。如果传递的参数partialStateOrMutator是函数，则直接执行，否则就通过mergeReactiveObjects方法合并到state中，最后生成subscriptionMutation对象，**通过triggerSubscriptions方法触发数据的更新**。
|
|
|
|
|
|
|
|
|
|
|
|
```javascript
|
|
|
|
|
|
function $patch(
|
|
|
|
|
|
partialStateOrMutator:
|
|
|
|
|
|
| _DeepPartial<UnwrapRef<S>>
|
|
|
|
|
|
| ((state: UnwrapRef<S>) => void)
|
|
|
|
|
|
): void {
|
|
|
|
|
|
let subscriptionMutation: SubscriptionCallbackMutation<S>
|
|
|
|
|
|
isListening = isSyncListening = false
|
|
|
|
|
|
// reset the debugger events since patches are sync
|
|
|
|
|
|
/* istanbul ignore else */
|
|
|
|
|
|
if (__DEV__) {
|
|
|
|
|
|
debuggerEvents = []
|
|
|
|
|
|
}
|
|
|
|
|
|
if (typeof partialStateOrMutator === 'function') {
|
|
|
|
|
|
partialStateOrMutator(pinia.state.value[$id] as UnwrapRef<S>)
|
|
|
|
|
|
subscriptionMutation = {
|
|
|
|
|
|
type: MutationType.patchFunction,
|
|
|
|
|
|
storeId: $id,
|
|
|
|
|
|
events: debuggerEvents as DebuggerEvent[],
|
|
|
|
|
|
}
|
|
|
|
|
|
} else {
|
|
|
|
|
|
mergeReactiveObjects(pinia.state.value[$id], partialStateOrMutator)
|
|
|
|
|
|
subscriptionMutation = {
|
|
|
|
|
|
type: MutationType.patchObject,
|
|
|
|
|
|
payload: partialStateOrMutator,
|
|
|
|
|
|
storeId: $id,
|
|
|
|
|
|
events: debuggerEvents as DebuggerEvent[],
|
|
|
|
|
|
}
|
|
|
|
|
|
}
|
|
|
|
|
|
nextTick().then(() => {
|
|
|
|
|
|
isListening = true
|
|
|
|
|
|
})
|
|
|
|
|
|
isSyncListening = true
|
|
|
|
|
|
// because we paused the watcher, we need to manually call the subscriptions
|
|
|
|
|
|
triggerSubscriptions(
|
|
|
|
|
|
subscriptions,
|
|
|
|
|
|
subscriptionMutation,
|
|
|
|
|
|
pinia.state.value[$id] as UnwrapRef<S>
|
|
|
|
|
|
)
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
|
|
然后定义partialStore对象去存储ID、$patch、Pinia实例，并且新增了subscribe方法。再调用reactive函数把partialStore包裹成响应式对象，通过pinia.\_s.set的方法实现store的挂载。
|
|
|
|
|
|
|
|
|
|
|
|
最后我们通过pinia.\_s.get获取的就是partialStore对象，defineStore返回的方法useStore就可以通过useStore去获取缓存的Pinia对象，实现对数据的更新和读取。
|
|
|
|
|
|
|
|
|
|
|
|
这里我们也可以看到，除了直接执行Action方法，还可以通过调用内部的 `count.$patch({count:count+1})` 的方式来实现数字的累加。
|
|
|
|
|
|
|
|
|
|
|
|
```javascript
|
|
|
|
|
|
const partialStore = {
|
|
|
|
|
|
_p: pinia,
|
|
|
|
|
|
// _s: scope,
|
|
|
|
|
|
$id,
|
|
|
|
|
|
$onAction: addSubscription.bind(null, actionSubscriptions),
|
|
|
|
|
|
$patch,
|
|
|
|
|
|
$reset,
|
|
|
|
|
|
$subscribe(callback, options = {}) {
|
|
|
|
|
|
const removeSubscription = addSubscription(
|
|
|
|
|
|
subscriptions,
|
|
|
|
|
|
callback,
|
|
|
|
|
|
options.detached,
|
|
|
|
|
|
() => stopWatcher()
|
|
|
|
|
|
)
|
|
|
|
|
|
const stopWatcher = scope.run(() =>
|
|
|
|
|
|
watch(
|
|
|
|
|
|
() => pinia.state.value[$id] as UnwrapRef<S>,
|
|
|
|
|
|
(state) => {
|
|
|
|
|
|
if (options.flush === 'sync' ? isSyncListening : isListening) {
|
|
|
|
|
|
callback(
|
|
|
|
|
|
{
|
|
|
|
|
|
storeId: $id,
|
|
|
|
|
|
type: MutationType.direct,
|
|
|
|
|
|
events: debuggerEvents as DebuggerEvent,
|
|
|
|
|
|
},
|
|
|
|
|
|
state
|
|
|
|
|
|
)
|
|
|
|
|
|
}
|
|
|
|
|
|
},
|
|
|
|
|
|
assign({}, $subscribeOptions, options)
|
|
|
|
|
|
)
|
|
|
|
|
|
)!
|
|
|
|
|
|
|
|
|
|
|
|
return removeSubscription
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
const store: Store<Id, S, G, A> = reactive(
|
|
|
|
|
|
assign({}， partialStore )
|
|
|
|
|
|
)
|
|
|
|
|
|
|
|
|
|
|
|
// store the partial store now so the setup of stores can instantiate each other before they are finished without
|
|
|
|
|
|
// creating infinite loops.
|
|
|
|
|
|
pinia._s.set($id, store)
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
|
|
**我们可以看出一个简单的store功能，真正需要支持生产环境的时候，也需要很多逻辑的封装。**
|
|
|
|
|
|
|
|
|
|
|
|
代码内部除了\_\_dev\_\_调试环境中对Devtools支持的语法，还有很多适配Vue 2的语法，并且同时支持Optipn风格和Composition风格去创建store。createSetupStore等方法内部也会通过Map的方式实现缓存，并且setActivePinia方法可以在多个Pinia实例的时候获取当前的实例。
|
|
|
|
|
|
|
|
|
|
|
|
这些思路在Vue、vue-router源码中都能看到类似的实现方式，这种性能优化的思路和手段也值得我们学习，在项目开发中也可以借鉴。
|
|
|
|
|
|
|
|
|
|
|
|
## 总结
|
|
|
|
|
|
|
|
|
|
|
|
最后我们总结一下今天学到的内容吧。由于课程之前的内容已经手写了一个迷你的Vuex，这一讲我们就越过Vuex4，直接去研究了Vuex5的提案。
|
|
|
|
|
|
|
|
|
|
|
|
Vuex5针对Vuex4中的几个痛点，去掉了容易混淆的概念Mutation，并且去掉了对TypeScript不友好的namespace功能，使用组合store的方式让Vuex对TypeScript更加友好。
|
|
|
|
|
|
|
|
|
|
|
|
Pinia就是Vuex5提案产出的框架，现在已经是Vue官方的框架了，也就是Vuex5的实现。在Pinia的代码中，我们通过createPinia创建Pinia实例，并且可以通过Option和Composition两种风格的API去创建store，返回 useStore 函数获取Pinia的实例后，就可以进行数据的修改和读取。
|
|
|
|
|
|
|
|
|
|
|
|
## 思考
|
|
|
|
|
|
|
|
|
|
|
|
最后留一个思考题吧。对于数据共享语法，还有provide/inject和自己定义的Composition，什么时候需要使用Pinia呢？
|
|
|
|
|
|
|
|
|
|
|
|
欢迎到评论区分享你的想法，也欢迎你把这一讲的内容分享给你的朋友们，我们下一讲再见！
|
|
|
|
|
|
|
