在上下文使用者上使用 useContext() 时反应上下文“属性‘状态’不存在”

Question

你有想念' td' $('#' + rowId)将是$('#' + rowId+ ' td') $('#' + rowId+ ' td').each(function() {     $('td').css('border-top', '1px solid #7f7f7f'); });我正在尝试在我的 React 项目中实现上下文。每次我尝试实现这个上下文时，我都会得到同样的错误：Property 'state' does not exist on type '{ count: number; currentColor: string; }'.  > 40 |   let { state, dispatch } = React.useContext(ContextOne);       |         ^上下文提供程序代码：import * as React from "react";let ContextOne = React.createContext(initialState);let initialState = {  count: 10,  currentColor: "#bada55"};let reducer = (state, action) => {  switch (action.type) {    case "reset":      return initialState;    case "increment":      return { ...state, count: state.count + 1 };    case "decrement":      return { ...state, count: state.count - 1 };    case "set-color":      return { ...state, currentColor: action.payload };  }};function ContextOneProvider(props) {  let [state, dispatch] = React.useReducer(reducer, initialState);  let value = { state, dispatch };  return (    <ContextOne.Provider value={value}>{props.children}</ContextOne.Provider>  );}let ContextOneConsumer = ContextOne.Consumer;export { ContextOne, ContextOneProvider, ContextOneConsumer };我尝试了许多在线示例上下文提供程序，但每次调用 useContext() 时，都会出现相同的错误。需要修改哪些内容才能使 Context 正常工作？

Answer 1

createContext参数类型应与您的值ContextOne.Provider类型匹配。您还需要改进您的类型以指导更多的TypeScript编译器：

import * as React from "react";

type State = {

  count: number

  currentColor: string

}

const initialState: State = {

  count: 10,

  currentColor: "#bada55",

};

type Context = {

  state: State

  dispatch: React.Dispatch<State>

}

const ContextOne = React.createContext<Context>({

  state: initialState,

  dispatch: () => {},

});

// You need to define the type Action

const reducer: React.Reducer<State, Action> = (state, action) => {

  switch (action.type) {

    case "reset":

      return initialState;

    case "increment":

      return { ...state, count: state.count + 1 };

    case "decrement":

      return { ...state, count: state.count - 1 };

    case "set-color":

      return { ...state, currentColor: action.payload };

  }

};

function ContextOneProvider(props) {

  const [state, dispatch] = React.useReducer(reducer, initialState);

  const value: Context = { state, dispatch };

  return (

    <ContextOne.Provider value={value}>{props.children} </ContextOne.Provider>

  );

}

let ContextOneConsumer = ContextOne.Consumer;

export { ContextOne, ContextOneProvider, ContextOneConsumer };

Answer 2

您的问题是您正在向具有属性的上下文提供者提供初始状态countand currentColor，而您提供的值（新状态）ContextOneProvider具有属性stateand dispatch。

我想您会希望将 initialState 交换为以下内容：

{

  state: null,

  dispatch: null,

}

如果您使用的是打字稿，您可能希望提供一个将这些作为可选参数的接口。