Question 282357 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – Error using Redux reducers when creating the store

When using Expo to build the app, I get this error:

Error: "reducer" is a required argument, and must be a function or an object of functions that can be passed to combineReducers, js engine: hermes

I am using combineReducers() to put all of them together and then creating the store with configureStore() since createStore() is deprecated.

this is my reducer bundler:

import { combineReducers } from "@reduxjs/toolkit";
import { commentReducer } from "./commentReducer.js";
import { lessonReducer } from "./lessonReducer.js";
import { studentReducer } from "./studentReducer.js";
import { subjectReducer } from "./subjectReducer.js";
import { tokenReducer } from "./tokenReducer.js";
import { userReducer } from "./userReducer.js";

export const rootReducer = combineReducers({
  user: userReducer,
  token: tokenReducer,
  subject: subjectReducer,
  student: studentReducer,
  lesson: lessonReducer,
  comment: commentReducer,
});

and this is where I create the store:

import { configureStore } from "@reduxjs/toolkit";
import rootReducer from "./reducers/rootReducer.js";

const store = configureStore({
  reducer: rootReducer,
});

export default store;

This is one of the reducers, they are all exactly the same because I just created them by copying to later on fill:


import * as types from "../actions/types";

const initialState = {
  token: "",
  loading: false,
  error: null,
};

export const tokenReducer = (state = initialState, action) => {
  switch (action.type) {
    case types.LOGIN_REQUEST:
      return { ...state, loading: true, error: null };

    case types.LOGIN_SUCCESS:
      return { ...state, loading: false, token: action.payload, error: null };

    case types.LOGIN_FAILURE:
      return { ...state, loading: false, error: action.payload, token: "" };

    default:
      return state;
  }
};

I tried commenting every single file where there is a reducer and still get the same error, any ideas on how I can fix it?

Tags:

2

Answers


  1. 0

    first of all: I think there is no need to combine reducers as configure store does this under the hood (RtK Docs)

    configureStore(): wraps createStore to provide simplified configuration options and good defaults. It can automatically combine your slice reducers, adds whatever Redux middleware you supply, includes redux-thunk by default, and enables use of the Redux DevTools Extension.

    Second thing: I think if you are going to use RTK, you should stick to the way of creating reducers mentioned in the Docs (ie: use createReducer function)

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  2. 0

    You are exporting as a named export, but importing a default export.

    You need to do

    import { rootReducer } from "./reducers/rootReducer.js";

    That said, the style of Redux you are writing here is 4+ years outdated at this point – modern Redux doesn’t use combineReducers, switch..case statements, ACTION_TYPES or hand-written immutable reducer update logic.

    Please read the official Redux Tutorial to learn modern Redux.

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