import React from 'react'
// 把源數(shù)據(jù)使用Proxy進(jìn)行代理處理,后面就可以精準(zhǔn)的去找到變化的數(shù)據(jù)
import { produce } from 'immer'
const state = {
  count: 1
}
// 進(jìn)行代理后，并修改
// draft就是代理對(duì)象，它就是state代理對(duì)象
const newState = produce(state, draft => {
  draft.count++
})
console.log(newState.count)// 2
const App = () => {
  return <div></div>
}
export default App

import React from 'react'
// 把源數(shù)據(jù)使用Proxy進(jìn)行代理處理,后面就可以精準(zhǔn)的去找到變化的數(shù)據(jù)
import { produce } from 'immer'
const baseState = {
  arr: [1, 2, 3],
  obj: { id: 1, name: '張三' }
}
// 使用immer進(jìn)行proxy代理，源數(shù)據(jù)中只有變化的了的數(shù)據(jù)才更新，沒有變化則共享，提高性能
const newState = produce(baseState, draft => {
  draft.arr.push(4)
})
// 當(dāng)前只修改數(shù)組，對(duì)象沒有修改，共享
console.log('arr', newState.arr === baseState.arr) // false
console.log('obj', newState.obj === baseState.obj) // true
const App = () => {
  return <div></div>
}
export default App

import React, { Component } from 'react'
import { produce } from 'immer'
// 優(yōu)化setState更新數(shù)據(jù)
class App extends Component {
  state = {
    count: 100,
    carts: [
      { id: 1, name: 'aa', num: 1 },
      { id: 2, name: 'bb', num: 2 }
    ]
  }
  addCount = () => {
    // 原來(lái)的寫法
    // this.setState(state => ({ count: state.count + 1 }))
    // 使用immer來(lái)優(yōu)化setState操作
    this.setState(
      produce(draft => {
        // 不用返回，返加不允許，draft它是一個(gè)代理對(duì)象，修改后，它能監(jiān)聽到數(shù)據(jù)的變化，更新視圖
        draft.count++
      })
    )
  }
  render() {
    return (
      <div>
        <h3>{this.state.count}</h3>
        <button onClick={this.addCount}>++++++</button>
        <hr />
        {this.state.carts.map((item, index) => (
          <li key={item.id}>
            <span>{item.name}</span>
            <span>---</span>
            <span>
              {item.num} --
              <button
                onClick={() => {
                  this.setState(
                    produce(draft => {
                      // draft它就是當(dāng)前的this.state
                      draft.carts[index].num++
                    })
                  )
                }}
              >
                ++++
              </button>
            </span>
          </li>
        ))}
      </div>
    )
  }
}
export default App

import React, { useState } from 'react'
import { produce } from 'immer'
const App = () => {
  // 普通的數(shù)字，不是proxy代理，proxy代理的是對(duì)象
  // 如果它是一個(gè)普通值，沒有必要使用immer來(lái)完成優(yōu)化操作
  let [count, setCount] = useState(100)
  // 對(duì)象類型才是使用immer工作的場(chǎng)景
  let [carts, setCarts] = useState([
    { id: 1, name: 'aa', num: 1 },
    { id: 2, name: 'bb', num: 2 }
  ])
  return (
    <div>
      <h3>{count}</h3>
      <button
        onClick={() => {
          // 之前的寫法
          // setCount(v => v + 1)
          setCount(produce(draft => draft + 1))
        }}
      >
        +++count+++
      </button>
      <hr />
      <button
        onClick={() => {
          setCarts(
            produce(draft => {
              draft.push({ id: Date.now(), num: 1, name: 'aaaa--' + Date.now() })
            })
          )
        }}
      >
        添加商品
      </button>
      {carts.map((item, index) => (
        <li key={item.id}>
          <span>{item.name}</span>
          <span>---</span>
          <span>
            {item.num} --
            <button
              onClick={() => {
                setCarts(
                  produce(draft => {
                    // 不能返回，寫上去感覺就像在vue的感覺
                    draft[index].num++
                  })
                )
              }}
            >
              ++++
            </button>
          </span>
          <span
            onClick={() => {
              setCarts(
                produce(draft => {
                  draft.splice(index, 1)
                })
              )
            }}
          >
            刪除
          </span>
        </li>
      ))}
    </div>
  )
}
export default App

import { createStore } from 'redux'
import { produce } from 'immer'
const initState = {
  count: 100
}
// 以前的寫法
/* const reducer = (state = initState, { type, payload }) => {
  if ('add' === type) {
    // 深復(fù)制
    return { ...state, count: state.count + payload }
  }
  return state
} */
const reducer = produce((draft, { type,  payload }) => {
  // 寫法就和vuex中的mutation中的寫法一樣的，簡(jiǎn)化了
  // 操作數(shù)據(jù)無(wú)需深復(fù)制，提升性能
  if ('add' === type) draft.count += payload
}, initState)
export default createStore(reducer)

import React from 'react'
import { useSelector, useDispatch } from 'react-redux'
const App = () => {
  const dispatch = useDispatch()
  const count = useSelector(state => state.count)
  return (
    <div>
      <h3>{count}</h3>
      <button
        onClick={() => {
          dispatch({ type: 'add', payload: 2 })
        }}
      >
        ++++
      </button>
    </div>
  )
}
export default App

import React from 'react'
import { useSelector, useDispatch } from 'react-redux'
const App = () => {
  const dispatch = useDispatch()
  const count = useSelector(state => state.count)
  return (
    <div>
      <h3>{count}</h3>
      <button
        onClick={() => {
          dispatch({ type: 'add', payload: 2 })
        }}
      >
        ++++
      </button>
    </div>
  )
}
export default App

import { configureStore } from '@reduxjs/toolkit'
// 上來(lái)它就是分模塊，在項(xiàng)目中，所以的數(shù)據(jù)一定是分模塊來(lái)管理的
import count from './modules/count'
import user from './modules/users'
export default configureStore({
  reducer: {
    count,
    user
  }
})

import { createSlice } from '@reduxjs/toolkit'
// 同步操作
const countSlice = createSlice({
  // 命名空間名稱，比redux中更好，redux沒有
  // 它的名稱要和入口文件中configureStore中的reducer配置對(duì)象中的key名稱要一致
  name: 'count',
  // 初始化數(shù)據(jù)源
  initialState: {
    num: 10 
  },
  // 修改數(shù)據(jù)源的方法集合
  reducers: {
    // 組件中派發(fā)dispatch(setNum(2)) // 2就會(huì)給payload
    // state它就是proxy對(duì)象[immer]
    setNum(state, { payload }) {
      state.num += payload
    }
  }
})
// 導(dǎo)出給在組件中調(diào)用
export const { setNum } = countSlice.actions
// 把當(dāng)前模塊的reducer導(dǎo)入，集合到大的reducer中
export default countSlice.reducer

import { createSlice, createAsyncThunk } from '@reduxjs/toolkit'
// 方案2
// 寫在上面,進(jìn)行網(wǎng)絡(luò)請(qǐng)求
export const fetchUser = createAsyncThunk('user/fetchUser', async page => {
  // 實(shí)現(xiàn)異步數(shù)據(jù)獲取
  let ret = await (await fetch('/api/users?page=' + page)).json()
  // return 中的數(shù)據(jù)就是返回到state中的users中的數(shù)據(jù)  一定要return
  return ret.data
})
// 異步操作
const userSlice = createSlice({
  name: 'user',
  initialState: {
    users: []
  },
  reducers: {
    setUsers(state, { payload }) {
      state.users = payload
    }
  },
  // 解決異步
  extraReducers: builder => {
    // 模擬了promise的3個(gè)狀態(tài)，只取成功狀態(tài) fulfilled
    // payload中的數(shù)據(jù)就是fetchUser方法它return出來(lái)的數(shù)據(jù)
    builder.addCase(fetchUser.fulfilled, (state, { payload }) => {
      state.users = payload
    })
  }
})
export const { setUsers } = userSlice.actions
// 網(wǎng)絡(luò)請(qǐng)求  --- 內(nèi)置redux-thunk所以，就可以在此處完成異步操作  -- 我推薦的
// 方案1
export const fetchThunkUser = () => async dispatch => {
  let ret = await (await fetch('/api/users')).json()
  dispatch(setUsers(ret.data))
}
export default userSlice.reducer