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javascriptreactjsreact-hooksuse-reducer

useReducer returning a promise instead of the updated state


My reducer:

export const initialUserState = {
    username: '',
    address: '',
    token: '',
    address: '',
    loggedIn: false,
    loaded: false,
};

export const userReducer = async (state, action) => {
    try {
        switch (action.type) {
            case 'LOAD':
                try {
                    const value = JSON.parse(await AsyncStorage.getItem('user_info'));
                    const newState = { ...state, ...value, loggedIn: true, loaded: true };
                    console.log('New State:', newState);

                    if (value !== null) {
                        return newState;
                    }
                } catch (error) {
                    return { ...state, loaded: true };
                }
                break;
            default:
                return state;
        }
    } catch (error) {
        console.log(error);
        return state;
    }
};

My App.js:

import { userReducer, initialUserState } from './reducer';

const App = () => {
    const [user, dispatch] = useReducer(userReducer, initialUserState);

    useEffect(() => {
        dispatch({ type: 'LOAD', ready: setReady });
    }, []);

    useEffect(() => {
        console.log('state user:', user);
    }, [user]);
}

export default App;

What happens is that in App.js, after the second useEffect is called, the state updates and user returns a promise. The promise has multiple properties, inside one of them is the correct state it was supposed to return. Shouldn't it return the state? Am I doing something wrong?

In a nutshell:

1) App starts

2) useEffect calls the first time and has the correct initial state

3) I call the LOAD action which will update the state

4) useEffect gets called the second time. This time it returns a promise, and it should return only the updated state of the store, I guess?

Console


Solution

  • It looks like the function you pass to useReducer is async. All async functions return a promise. You would need to await or use .then syntax to get the value from the promise. It's not a promise the first time through because it returns initial state. Hope that helps!