import { createAsyncThunk, createSlice, PayloadAction } from '@reduxjs/toolkit';
import { RootState, AppThunk } from '../../app/store';
import { fetchCount } from './counterAPI';
export interface CounterState {
value: number;
status: 'idle' | 'loading' | 'failed';
}
const initialState: CounterState = {
value: 0,
status: 'idle',
};
// The function below is called a thunk and allows us to perform async logic. It
// can be dispatched like a regular action: `dispatch(incrementAsync(10))`. This
// will call the thunk with the `dispatch` function as the first argument. Async
// code can then be executed and other actions can be dispatched. Thunks are
// typically used to make async requests.
export const incrementAsync = createAsyncThunk(
'counter/fetchCount',
async (amount: number) => {
const response = await fetchCount(amount);
// The value we return becomes the `fulfilled` action payload
return response.data;
}
);
export const counterSlice = createSlice({
name: 'counter',
initialState,
// The `reducers` field lets us define reducers and generate associated actions
reducers: {
increment: (state) => {
// Redux Toolkit allows us to write "mutating" logic in reducers. It
// doesn't actually mutate the state because it uses the Immer library,
// which detects changes to a "draft state" and produces a brand new
// immutable state based off those changes
state.value += 1;
},
decrement: (state) => {
state.value -= 1;
},
// Use the PayloadAction type to declare the contents of `action.payload`
incrementByAmount: (state, action: PayloadAction<number>) => {
state.value += action.payload;
},
},
// The `extraReducers` field lets the slice handle actions defined elsewhere,
// including actions generated by createAsyncThunk or in other slices.
extraReducers: (builder) => {
builder
.addCase(incrementAsync.pending, (state) => {
state.status = 'loading';
})
.addCase(incrementAsync.fulfilled, (state, action) => {
state.status = 'idle';
state.value += action.payload;
})
.addCase(incrementAsync.rejected, (state) => {
state.status = 'failed';
});
},
});
export const { increment, decrement, incrementByAmount } = counterSlice.actions;
// The function below is called a selector and allows us to select a value from
// the state. Selectors can also be defined inline where they're used instead of
// in the slice file. For example: `useSelector((state: RootState) => state.counter.value)`
export const selectCount = (state: RootState) => state.counter.value;
// We can also write thunks by hand, which may contain both sync and async logic.
// Here's an example of conditionally dispatching actions based on current state.
export const incrementIfOdd =
(amount: number): AppThunk =>
(dispatch, getState) => {
const currentValue = selectCount(getState());
if (currentValue % 2 === 1) {
dispatch(incrementByAmount(amount));
}
};
export default counterSlice.reducer;