How I send custom parameters on `createAsyncThunk` on "pending" status?

Question

When fetchUserById() is created its output response is defined.

const fetchUserById = createAsyncThunk<{user: UserInterface, id: number}, number>(
  'users/fetchByIdStatus',
  async (userId) => {
    const response = await userAPI.fetchById(userId)
    return {user: response.data, id: userId}
  }
);

const userSlice = createSlice({
  name: "users",
  initialState: [],
  reducers: {},
  extraReducers: (builder) => {
    builder.addCase(fetchUserById.pending, (state, { payload }) => {
      // how I configured custom value for this payload?
      // I need to send the user id.
    });
    builder.addCase(fetchUserById.fulfilled, (state, {payload}) => {
      /**
       * @var {UserInterface} user
       * @var {number} id;
       */
      const {id, user} = payload;
      state[id].loading = false;
      state[id].user = user;
    });
  },
});

But how can I define a response when the action is on "pending" state?

Answer 1

The arg that you pass into createAsyncThunk will be available in action.meta.arg. So in your example, you could reference that like this:

builder.addCase(fetchUserById.pending, (state, { meta }) => {
      console.log(meta.arg); // meta.arg will have whatever value was passed as `userId`
    });