reactjs - 提供程序值的 Typescript React UseReducer 类型错误

Question

我目前在使用 Typescript 中的 React Context API 让我的提供者工作时遇到错误，我收到以下错误，

Type '{ state: { hasEnterPressed: boolean; searchQuery: string; }; dispatch: Dispatch<stringAction>; }' 
is missing the following properties from type '{ hasEnterPressed: boolean; searchQuery: string; dispatch: 
(state: { hasEnterPressed: boolean; searchQuery: string; }, action: stringAction) => 
{ hasEnterPressed: boolean; searchQuery: string; }; }': hasEnterPressed, searchQuery  TS2739

    50 | 
    51 |     return (
  > 52 |         <SearchContext.Provider value={value}>
       |                                 ^
    53 |             {props.children}
    54 |         </SearchContext.Provider>
    55 |     )

我认为这与我的 CreateContext 调用的构造有关，这就是我可能遇到问题的原因。我已经尝试构建接口(interface)类型，但我仍然遇到同样的错误。

import React, {useReducer, createContext, Dispatch}  from "react";


export interface Action {
    type: string
}

export interface stringAction extends Action {
    payload: string
}

export interface reducerState {
    hasEnterPressed: boolean
    searchQuery: string,
}


const reducer = (state: reducerState, action: stringAction) => {
    switch(action.type) {
        case "UPDATEKEYPRESS":
            return {
                ...state,
                hasEnterPressed: false
            };
        case "UPDATESEARCHQUERY":
            return {
                ...state,
                searchQuery: action.payload
            }
        default:
            throw new Error();
    }
}

const initalState: reducerState = {
    hasEnterPressed: false,
    searchQuery : '',
}


export const SearchContext = createContext<reducerState>(initalState);

export const SearchProvider: React.FC = (props) => {

    const [state, dispatch] = useReducer(reducer, initalState)

    const value = {state, dispatch}

    return (
        <SearchContext.Provider value={value}>
            {props.children}
        </SearchContext.Provider>
    )
}

export default SearchProvider;

Answer 1

value你传入的是一个对象{state, dispatch}同时createContext<reducerState>使提供者期望它是 reducerState .

您需要将上下文类型更改为

interface SearchContextValue {
  state: reducerState; 
  dispatch: Dispatch<ReducerAction<typeof reducer>>
}

export const SearchContext = createContext<SearchContextValue>({
 state: initalState, 
 dispatch: () => {} // fake, but it is not possible to provide at this point 
});

或者如果您不需要传递调度——传递状态作为值

<SearchContext.Provider value={state}>

请注意，最好将类型名称大写，否则很难将它们与变量名称区分开来。