javascript - Redux 操作 typescript 返回类型不起作用

Question

所以基本上我试图返回一组函数的类型并能够在我的 redux reducer 中匹配它。

这是我的尝试:

Action .ts

export const SET_CART_ITEMS = "SET_CART_ITEMS";
export const SET_CART_TOTALS = "SET_CART_TOTALS";

export const ADD_CART_ITEM = "ADD_CART_ITEM";
export const REMOVE_CART_ITEM = "REMOVE_CART_ITEM";

export const SET_CART_LOADING = "SET_CART_LOADING";

export function setCart(cart: Cart) {
  return {
    type: SET_CART_ITEMS,
    cart
  } as const;
}

export function setTotals(totals: CartTotal) {
  return {
    type: SET_CART_TOTALS,
    totals
  }
}

export function addCartItem(cart: Cart) {
  return {
    type: ADD_CART_ITEM,
    cart
  } as const;
}

export function removeCartItem(cart: Cart) {
  return {
    type: REMOVE_CART_ITEM,
    cart
  } as const;
}

export function toggleCartLoading(loading: boolean) {
  return {
    type: SET_CART_LOADING,
    loading
  } as const;
}

export type CartActions = ReturnType<typeof setCart>| ReturnType<typeof addCartItem> | ReturnType<typeof removeCartItem> | ReturnType<typeof toggleCartLoading> | ReturnType<typeof setTotals>

reducer .ts

import { 
   CartActions,  
   ADD_CART_ITEM,
   REMOVE_CART_ITEM,
   SET_CART_ITEMS,
   SET_CART_TOTALS,
   SET_CART_LOADING 
} from '../../../actions';

export default (state: CartState = initialState, action: CartActions) : CartState => {
  switch (action.type) {
    case ADD_CART_ITEM:
      return {
        ...state,
        cart: {
          ...action.cart
        }
      }
    case REMOVE_CART_ITEM:
      return {
        ...state,
        cart: {
          ...action.cart
        }
      }
    case SET_CART_ITEMS:
      return {
        ...state,
        cart: action.cart
      }
    case SET_CART_TOTALS:
      return {
        ...state,
        totals: action.totals
      }
    case SET_CART_LOADING:
      return {
        ...state,
        loading: action.loading
      }
    default:
      break;
  }
  return state;
}

这根本不起作用，我收到的错误是在 reducer 开关中说:

"Property 'cart' does not exist on type 'CartActions'.
  Property 'cart' does not exist on type '{ type: string; totals: CartTotal; }'."


Property 'loading' does not exist on type '{ readonly type: "SET_CART_ITEMS"; readonly cart: Record<string, CartItem>; } | { readonly type: "ADD_CART_ITEM"; readonly cart: Record<string, CartItem>; } | { ...; } | { ...; } | { ...; }'.
  Property 'loading' does not exist on type '{ readonly type: "SET_CART_ITEMS"; readonly cart: Record<string, CartItem>; }'.ts(2339)

我是否遗漏了一些明显的东西？我真的希望不需要通过界面手动输入所有操作。

灵感来自 https://gist.github.com/schettino/c8bf5062ef99993ce32514807ffae849

Answer 1

每个 Action 创建者返回类型都必须用as const注释，以便TS可以在reducer的switch语句中区分您的 Action 。

在 setTotals 中，这个 const 断言似乎丢失了 - 至少提供的代码在 playground 中再次工作。 ，添加后。

您可以创建一个通用操作创建器以使其更具可扩展性并省略 as const:

function createAction<T extends string, U, K extends string>(type: T, key: K, payload: U) {
  return ({
    type,
    [key]: payload
  }) as { type: T; } & { [P in K]: U }
  // need to cast, so TS doesn't return a widened index signature type
}

export function setTotals(totals: CartTotal) {
  return createAction(SET_CART_TOTALS, "totals", totals)
}
// same with the other functions

Code sample in Playground