react useContext createContext 方法使用

还是上一篇的例子，我把 代码改下

import React, { useReducer } from 'react'
import { useContext } from "react"

// 创建上下文
const Context = React.createContext();
//此时state 就是 count 
function countReducer(state, action) {

    switch (action.type) {
        case "add":
            state++;
            return state;
            break;
        case "minus":
            state--;
            return state;
            break;
        default:
            return state;
    }
}


const Cart = () => {
    const [state, dispatch] = useReducer(countReducer, 0);
    return (
        <Context.Provider value={
   import React, { useRe