带有 redux-thunk 的类型安全的 useDispatch

Question

我正在使用 redux-thunk 来使用异步操作创建器。结果也返回给相应的调用者。

function fetchUserName(userId: number): Promise<string> {
  return Promise.resolve(`User ${userId}`)
}

function requestUserName(userId: number) {
  return (dispatch: Dispatch) => {
    return fetchUserName(userId).then(name => {
      dispatch({
        type: 'SET_USERNAME',
        payload: name,
      })
    })
  }
}

这样，存储就更新了，同时允许组件直接处理响应。

function User() {
  const dispatch = useDispatch()
  useEffect(() => {
    dispatch(requestUserName(1))
      .then(name => {
        console.log(`user name is ${name}`)
      })
      .catch(reason => {
        alert('failed fetching user name')
      })
  }, [])
}

这是按预期工作的，但由于类型无效，它不会被 TypeScript 编译。

useDispatch 返回的 dispatch 未被识别为 returns Promise 的函数，因此 TypeScript 认为 Property 'then' does not exist on type '(dispatch: Dispatch<AnyAction>) => Promise<void>'..
即使可以识别，Promise 也应该正确输入

这种情况如何解决？

我可以围绕 useDispatch 创建一个包装器或重新定义 dispatch 的类型，但我不知道在这种特定情况下该类型应该是什么样子。

非常感谢您的任何建议。

Answer 1

useDispatch returns Dispatch 类型 used by Redux, so you can only dispatch standard actions with it. To also dispatch thunk actions, declare its type as ThunkDispatch（来自 redux-thunk）。

ThunkDispatch 接收存储状态的类型参数，extra thunk args and your action type. It allows to dispatch a ThunkAction，这基本上是 requestUserName.

的内部函数

例如，您可以这样输入：

import { ThunkDispatch } from "redux-thunk";
import { AnyAction } from "redux";

type State = { a: string }; // your state type
type AppDispatch = ThunkDispatch<State, any, AnyAction>; 
// or restrict to specific actions instead of AnyAction

function User() {
  const dispatch: AppDispatch = useDispatch();
  useEffect(() => {
    dispatch(requestUserName(1))
      .then(...)  // works now
  }, []);
  ...
}

AppDispatch 也可以 inferred 从商店 typeof store.dispatch:

import thunk, { ThunkDispatch, ThunkMiddleware } from "redux-thunk";

const mw: ThunkMiddleware<State, AnyAction> = thunk;
const dummyReducer = (s: State | undefined, a: AnyAction) => ({} as State);
const store = createStore(dummyReducer, applyMiddleware(mw));

type AppDispatch = typeof store.dispatch // <-- get the type from store

TS Playground sample

另请参阅 redux 关于使用带钩子的打字稿的文档：https://redux.js.org/usage/usage-with-typescript#define-typed-hooks

Answer 2

我的常用设置包括类型安全 AppDispatch 和类型挂钩；

import { createStore, applyMiddleware, PreloadedState, combineReducers } from 'redux';
import { TypedUseSelectorHook, useDispatch, useSelector } from 'react-redux';
import thunk, { ThunkDispatch } from 'redux-thunk';
import { composeWithDevTools } from 'redux-devtools-extension';

const middlewares = [thunk];
const enhancer = composeWithDevTools({ /* optional actionsBlacklist, etc */ });

const reducers = combineReducers({ /* ... */ })
export type RootState = ReturnType<typeof reducers>;

export const initStore = (initState?: PreloadedState<RootState>) =>
  createStore(reducers, initState, enhancer(applyMiddleware(...middlewares)));
export const store = initStore();

export const useAppSelector: TypedUseSelectorHook<RootState> = useSelector;
type AppAction = ReturnType<typeof store.dispatch>;
export type AppDispatch = ThunkDispatch<RootState, any, AppAction>;
export const useAppDispatch = () => useDispatch<AppDispatch>();

请注意，Redux Toolkit 会略有不同，因为您 configureStore 而不是 combineReducers

带有 redux-thunk 的类型安全的 useDispatch

type-safe useDispatch with redux-thunk

typescript

redux

redux-thunk