Vuex 2.0 about Vue.js 2.0 The knowledge base you need to update

Application Structure

In fact, Vuex has no restrictions on how to organize your code structure. On the contrary, it enforces a series of high-level principles:

1. Application-level status is concentrated in the store.

2. The only way to change the state is to submit mutations, which is a synchronous transaction.

3. Asynchronous logic should be encapsulated in action.

As long as you follow these rules, it's up to you how you structure your project. If your store file is very large, just split it into action, mutation and getter files.

For slightly more complex applications, we may need to use modules. The following is a simple project structure:

├── index.html
├── main.js
├── api
│ └── ... # Initiate API request here
├── components
│ ├─ ─ app.Vuep│ └ ── ...
└ ─
└ ─ ─ ─ i ├ ├ ─ — Actions.js # ├ ─ ─ ─ ─ ─ ─ ─ ─ Mutations
└── modules
├── cart.js └── cart.js └── products.js # products module


For more, check out the shopping cart example.

Modules

Due to the use of a single state tree, all the state of the application is contained in one large object. However, as the scale of our application continued to grow, this Store became very bloated.

In order to solve this problem, Vuex allows us to divide the store into modules. Each module contains its own state, mutation, action and getter, even nested modules. This is how it is organized:

const moduleA = {
 state: { ... },
 mutations: { ... },
 actions: { ... },
 getters: { ... }
}
 
const moduleB = {
 state: { ... },
 mutations: { ... },
 actions: { ... }
}
 
const store = new Vuex.Store({
 modules: {
 a: moduleA,
 b: moduleB
 }
})
 
store.state.a // -> moduleA's state
store.state.b // -> moduleB's state

Module local state

The mutations and getters methods of the module are the first to receive parameters Is the local state of the module.

const moduleA = {
 state: { count: 0 },
 mutations: {
 increment: (state) {
  // state 是模块本地的状态。
  state.count++
 }
 },
 
 getters: {
 doubleCount (state) {
  return state.count * 2
 }
 }
}

Similarly, in the module's actions, context.state exposes the local state, and context.rootState exposes the root state.

const moduleA = {
 // ...
 actions: {
 incrementIfOdd ({ state, commit }) {
  if (state.count % 2 === 1) {
  commit('increment')
  }
 }
 }
}

In the getters of the module, the root state is also exposed as the third parameter.

const moduleA = {
 // ...
 getters: {
 sumWithRootCount (state, getters, rootState) {
  return state.count + rootState.count
 }
 }
}

Namespace

Please note that the actions, mutations and getters within the module are still registered in the global namespace - this will allow multiple modules to respond to the same mutation/action type. You can add a prefix or suffix to the module name to set the namespace to avoid naming conflicts. If your Vuex module is reusable and the execution environment is unknown, then you should do this. Distance, we want to create a todos module:

// types.js
 
// 定义 getter、 action 和 mutation 的常量名称
// 并且在模块名称上加上 `todos` 前缀
export const DONE_COUNT = 'todos/DONE_COUNT'
export const FETCH_ALL = 'todos/FETCH_ALL'
export const TOGGLE_DONE = 'todos/TOGGLE_DONE'
// modules/todos.js
import * as types from '../types'
 
// 用带前缀的名称来定义 getters, actions and mutations
const todosModule = {
 state: { todos: [] },
 
 getters: {
 [types.DONE_COUNT] (state) {
  // ...
 }
 },
 
 actions: {
 [types.FETCH_ALL] (context, payload) {
  // ...
 }
 },
 
 mutations: {
 [types.TOGGLE_DONE] (state, payload) {
  // ...
 }
 }
}

Register a dynamic module

You can use the store.registerModule method to register a module after the store is created:

store.registerModule('myModule', {
 // ...
})

module’s store.state. myModule is exposed as the module's state.

Other Vue plug-ins can attach a module to the application store, and then use Vuex's state management function through dynamic registration. For example, the vuex-router-sync library integrates vue-router and vuex by managing the routing state of the application in a dynamically registered module.

You can also use store.unregisterModule(moduleName) to remove dynamically registered modules. But you cannot use this method to remove static modules (that is, modules declared when the store is created).

Plugins

Vuex’s store receives the plugins option, which exposes hooks for each mutation. A Vuex plug-in is a simple method that accepts sotre as the only parameter:

const myPlugin = store => {
 // 当 store 在被初始化完成时被调用
 store.subscribe((mutation, state) => {
 // mutation 之后被调用
 // mutation 的格式为 {type, payload}。
 })
}

Then use it like this:

const store = new Vuex.Store({
 // ...
 plugins: [myPlugin]
})

Submit Mutations within the plug-in

Plugins cannot directly modify the state - this is Like your components, they can only be changed by mutations.

By submitting mutations, the plug-in can be used to synchronize the data source to the store. For example, in order to synchronize the websocket data source to the store (this is just an example to illustrate the usage, in practice, the createPlugin method will be appended with more options to complete complex tasks).

export default function createWebSocketPlugin (socket) {
 return store => {
 socket.on('data', data => {
  store.commit('receiveData', data)
 })
 store.subscribe(mutation => {
  if (mutation.type === 'UPDATE_DATA') {
  socket.emit('update', mutation.payload)
  }
 })
 }
}

const plugin = createWebSocketPlugin(socket)
 
const store = new Vuex.Store({
 state,
 mutations,
 plugins: [plugin]
})

Generate status snapshot

Sometimes the plug-in wants to get the status "snapshot" and the changes before and after the status change. In order to implement these functions, a deep copy of the state object is required:

const myPluginWithSnapshot = store => {
 let prevState = _.cloneDeep(store.state)
 store.subscribe((mutation, state) => {
 let nextState = _.cloneDeep(state)
 
 // 对比 prevState 和 nextState...
 
 // 保存状态，用于下一次 mutation
 prevState = nextState
 })
}

** The plug-in that generates the state snapshot can only be used during the development phase. Use Webpack or Browserify and let the build tool handle it for us:

const store = new Vuex.Store({
 // ...
 plugins: process.env.NODE_ENV !== 'production'
 ? [myPluginWithSnapshot]
 : []
})

The plug-in will be enabled by default. To ship to production, you need to use Webpack's DefinePlugin or Browserify's envify to convert process.env.NODE_ENV !== 'production' to false.

Built-in Logger plug-in

如果你正在使用 vue-devtools，你可能不需要。

Vuex 带来一个日志插件用于一般的调试:

import createLogger from 'vuex/dist/logger'
 
const store = new Vuex.Store({
 plugins: [createLogger()]
})

   

createLogger 方法有几个配置项：

const logger = createLogger({
 collapsed: false, // 自动展开记录 mutation
 transformer (state) {
 // 在记录之前前进行转换
 // 例如，只返回指定的子树
 return state.subTree
 },
 mutationTransformer (mutation) {
 // mutation 格式 { type, payload }
 // 我们可以按照想要的方式进行格式化
 return mutation.type
 }
})

   

日志插件还可以直接通过 3f1c4e4b6b16bbbd69b2ee476dc4f83a 标签, 然后它会提供全局方法 createVuexLogger 。

要注意，logger 插件会生成状态快照，所以仅在开发环境使用。

严格模式

要启用严格模式，只需在创建 Vuex store 的时候简单地传入 strict: true。

const store = new Vuex.Store({
 // ...
 strict: true
})

   

在严格模式下，只要 Vuex 状态在 mutation 方法外被修改就会抛出错误。这确保了所有状态修改都会明确的被调试工具跟踪。

开发阶段 vs. 发布阶段

不要在发布阶段开启严格模式！ 严格模式会对状态树进行深度监测来检测不合适的修改 —— 确保在发布阶段关闭它避免性能损耗。
跟处理插件的情况类似，我们可以让构建工具来处理：

const store = new Vuex.Store({
 // ...
 strict: process.env.NODE_ENV !== 'production'
})