Redux如何设置初始状态

Question

我正在开发一个包含 React、Redux 和 TypeScript 的项目。

由于 TypeScript 的类型限制，我无法弄清楚如何设置初始状态。有人知道如何设置类型吗？

为简单起见，我将所有内容压缩在一个文件中，稍后将分成单独的文件。

state/index.ts

import { Notes } from '@material-ui/icons'
import { createStore, combineReducers } from 'redux'

// Types
type Note = {
    title: string
    description: string
}

type NoteState = {
    notes: Array<Note>
}

type NoteAction = {
    type: string
    payload: Note
}

type CountState = {
    count: number
}

type CountAction = {
    type: string
    payload: number
}

// Actions
const ADD_NOTE = 'ADD_NOTE'
const addNote: (note: Note) => NoteAction = (n) => ({ type: ADD_NOTE, payload: n })

const INCREMENT = 'INCREMENT'
const increment: (n: number) => CountAction = (n) => ({ type: INCREMENT, payload: n + 1 })

// Reducer
const noteReducer: (s: NoteState, a: NoteAction) => NoteState = (s = { notes: [] }, a) => {
    switch (a.type) {
        case ADD_NOTE:
            return { notes: [...s.notes, a.payload] }
        default:
            return s
    }
}

const countReducer: (s: CountState, a: CountAction) => CountState = (s = { count: 0 }, a) => {
    switch (a.type) {
        case INCREMENT:
            return { count: a.payload }
        default:
            return s
    }
}

const rootReducer = combineReducers({
    notes: noteReducer,
    counter: countReducer,
})

type RootState = ReturnType<typeof rootReducer>

// Store
const state = createStore(rootReducer({ notes: [], counter: 0 }, null))

错误 初始化状态对象时，IDE报错：

No overload matches this call.
  Overload 1 of 2, '(reducer: Reducer<unknown, Action<any>>, enhancer?: StoreEnhancer<unknown, unknown> | undefined): Store<unknown, Action<any>>', gave the following error.
    Argument of type 'CombinedState<{ notes: never; counter: never; }>' is not assignable to parameter of type 'Reducer<unknown, Action<any>>'.
      Type 'CombinedState<{ notes: never; counter: never; }>' provides no match for the signature '(state: unknown, action: Action<any>): unknown'.
  Overload 2 of 2, '(reducer: Reducer<unknown, Action<any>>, preloadedState?: {} | undefined, enhancer?: StoreEnhancer<unknown, {}> | undefined): Store<unknown, Action<any>>', gave the following error.
    Argument of type 'CombinedState<{ notes: never; counter: never; }>' is not assignable to parameter of type 'Reducer<unknown, Action<any>>'.ts(2769)

我需要在 createStore 函数中设置 App State。因为稍后会有一个函数从本地存储中检索 App State 并通过 createStore 方法传递。但我想先完成这项工作。有人有使用 Redux + TypeScript 的经验吗？

Answer 1

看来您为 createStore 函数输入了错误的参数。它将rootReducer 作为第一个参数，初始状态作为第二个参数，但是您将调用rootReducer 的结果设置为第一个参数。修改如下：

interface AppState {
  notes: NoteState;
  counter: CountState;
}

const rootReducer = combineReducers<AppState>({
  notes: noteReducer,
  counter: countReducer
});

const state = createStore(rootReducer, {
  notes: { notes: [] },
  counter: {
    count: 0
  }
});

还有一点需要注意，第一个状态参数可能是未定义的，所以你必须设置它可以是undefined：

const noteReducer: (s: NoteState | undefined, a: NoteAction) => NoteState = (

注意：这里是供你乱搞的代码框：https://codesandbox.io/s/inspiring-sound-0lh92?file=/src/store.ts:1178-1276