A simple implementation method of redux (code)

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Introduction: Handwritten implementation of redux/react-redux basic api

redux api

createStore(reducer, [preloadedState], enhancer)

创建一个 Redux store 来以存放应用中所有的 state
reducer (Function): 接收两个参数，当前的 state 树/要处理的 action，返回新的 state 树
preloadedState: 初始时的 state
enhancer (Function): store creator 的高阶函数，返回一个新的强化过的 store creator

Store method

getState() 返回应用当前的 state 树
dispatch(action) 分发 action。这是触发 state 变化的惟一途径
subscribe(listener) 添加一个变化监听器。每当 dispatch action 的时候就会执行，state 树中的一部分可能已经变化
replaceReducer(nextReducer) 替换 store 当前用来计算 state 的 reducer

combineReducers(reducers)

把一个由多个不同 reducer 函数作为 value 的 object，合并成一个最终的 reducer 函数

import { combineReducers } from 'redux'
import todos from './todos'
import counter from './counter'

export default combineReducers({
  todos,
  counter
})

applyMiddleware(...middleware)

使用包含自定义功能的 middleware 来扩展 Redux 是
...middleware (arguments): 遵循 Redux middleware API 的函数。每个 middleware 接受 Store 的 dispatch 和 getState 函数作为命名参数，并返回一个函数。该函数会被传入 被称为 next 的下一个 middleware 的 dispatch 方法，并返回一个接收 action 的新函数，这个函数可以直接调用 next(action)，或者在其他需要的时刻调用，甚至根本不去调用它。调用链中最后一个 middleware 会接受真实的 store 的 dispatch 方法作为 next 参数，并借此结束调用链。所以，middleware 的函数签名是 ({ getState, dispatch }) => next => action

import { createStore, combineReducers, applyMiddleware } from 'redux'
import thunk from 'redux-thunk'
import * as reducers from './reducers'

let reducer = combineReducers(reducers)
// applyMiddleware 为 createStore 注入了 middleware:
let store = createStore(reducer, applyMiddleware(thunk))

bindActionCreators(actionCreators, dispatch)

compose(...functions)

Compose multiple combinations from right to left function.
When multiple store enhancers need to be executed in sequence, you need to use it

import { createStore, applyMiddleware, compose } from 'redux'
import thunk from 'redux-thunk'
import DevTools from './containers/DevTools'
import reducer from '../reducers'

const store = createStore(
  reducer,
  compose(
    applyMiddleware(thunk),
    DevTools.instrument()
  )
)

Implement a simple redux

Use redux to implement

// import { createStore } from 'redux'
// 将redux文件替换成自己实现的redux文件
   import { createStore } from './self-redux.js'

// 这就是reducer处理函数，参数是状态和新的action
function counter(state=0, action) {
  // let state = state||0
  switch (action.type) {
    case '加机关枪':
      return state + 1
    case '减机关枪':
      return state - 1
    default:
      return 10
  }
}
// 新建store
const store = createStore(counter)
const init = store.getState()
console.log(`一开始有机枪${init}把`)
function listener(){
  const current = store.getState()
  console.log(`现在有机枪${current}把`)
}
// 订阅，每次state修改，都会执行listener
store.subscribe(listener)
// 提交状态变更的申请
store.dispatch({ type: '加机关枪' })

Implement createStore, store related methods

./self-redux.js

export function createStore(reducer) {
  let currentState = {}
  let currentListeners = []
  function getState() {
    return currentState
  }
  function subscribe(listeners) {
    currentListeners.push(listener)
  }
  function dispatch(action) {
    currentState = reducer(currentState, action)
    currentListeners.forEach(v => v())
    return action
  }
  dispatch({ type: '@rainie/init-store' })
  return {
    getState,
    subscribe,
    dispatch
  }
}

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