useCallBackReducer

import { useEffect, useRef, useReducer } from 'react'

const useCallBackReducer = (reducer, initialState) => {
	const [state, dispatch] = useReducer(reducer, initialState)
	const isUpdate = useRef()
	useEffect(() => {
		if (isUpdate.current) {
			// 不设置回调函数的话 isUpdate.current 是undefined,所以不会执行
			isUpdate.current(state)
		}
	}, [state])
	const useDispatch = (action, cb) => {
		//劫持dispatch,将回调函数赋予isUpdate.current
		//状态更新后会执行回调函数，在回调函数第一个参数可以获取到最新的状态
		isUpdate.current = cb
		dispatch(action)
	}

	return [state, useDispatch]
}

export default useCallBackReducer