reactjs - 类型 '{}' 上不存在属性

Question

我正在尝试在我的 React 应用程序中使用 Typescript

在我的 mapStateToProps 中我有这段代码

const mapStateToProps = (state: AppState) => {
    console.log(state)
    return {
        ...state.player,
        position: state.player.position
    }
}

我的应用状态

import { combineReducers } from 'redux';
import playerReducer from './player';

export const rootReducer = combineReducers({
  player: playerReducer
} as any);

export type AppState = ReturnType<typeof rootReducer>

我收到一个错误 TypeScript 错误:属性“player”在类型“{}”上不存在。 TS2339 与行 ...state.player 相关但是如果我 console.log 状态(在那之前的那一行)我的 state 有 player 属性。

我不确定为什么会收到此错误。我们将不胜感激。

玩家 reducer

import { Action } from '../actions/types';
import { Store } from '../types';


export const initialState: Store = {
  position: [410, 0]
};


const playerReducer = (state = initialState, action: Action) => {
  switch (action.type) {
    case 'MOVE_PLAYER':
      return {
        ...state,
        position: action.payload
      }   
    default:
      return state;
  }
}

export default playerReducer;

Answer 1

问题是 combineReducers 由于 as any 无法推断您传入的对象的类型。这意味着您的根 reducer 只能按类型推断:

const rootReducer: Reducer<{}, AnyAction>;

简单地取出combineReducers中的as any:

export const rootReducer = combineReducers({
  player: playerReducer
});

应该推断为:

const rootReducer: Reducer<{
  player: PlayerState;
}, AnyAction>;

---

尝试对您的 playerReducer 进行强类型化:

import { Action, Reducer } from "redux";

const playerReducer: Reducer<Store, Action> = (state = initialState, a) => {
    ...
};

我在我的项目中使用的 exact 模式是这样的(当然，您可能想要调整它，直到您得到更适合您的项目的东西):

import { Action, Reducer } from "redux";
import { MOVE_PLAYER } from "../actions/playerActions"; // list all relevant actions here

export interface PlayerState {
  readonly position: [number, number];
}

const initialState: PlayerState = {
  position: [410, 0];
};

const reducers: { [k: string]: (s: PlayerState, a: any) => PlayerState } = {
  [MOVE_PLAYER]: (s, a: { payload: [number, number] }) => ({ ...s, position: a.payload }),
  // other player reducers
}

const reducer: Reducer<PlayerState, Action> = (s = initialState, a) => {
  const f = reducers[a.type];
  return typeof f === "function" ? f(s, a) : s;
};
export default reducer;