redux-saga-callback

In a normal flow of a redux-saga application there might be some cases that you want get notified when a saga triggered by a dispatched action is completed. The purpose of this library is to provide some helper functions to achieve that functionalities.

Install

npm i redux-saga-callback

Usage

import { putWait, withCallback } from 'redux-saga-callback';

Wrap your saga generator with withCallback

takeEvery('FETCH_USERS', withCallback(fetchUsers));

Defined callback in your action if you need

dispatch({type: 'FETCH_USERS', onComplete: ({error, cancelled, data}) => {

}})

In saga you can wait for it (no callback definition is needed with putWait)

const users = yield putWait({type: 'FETCH_USERS'});

API

withCallback

This is a higer order saga which will call the onComplete callback property of the action if defined.

onComplete

• error: error which is thrown by the saga
• cancelled: Will be true if the saga is cancelled
• data: the data returned by the saga

function onComplete({ error, cancelled, data }) {
    /* handle callback */
}

function* fetchUsers() {
    const users = yield fetch('/users');

    // put users to store
    yield put(putUsers(users));

    // returned value will be passed to onComplete function as parameter
    // Exceptions will be handled by the withCallback and will also be passed to onComplete
    return users;
}

export function*(){
    yield all([
        takeEvery('FETCH_USERS', withCallback(fetchUsers))
    ])
}

// userSaga.js

// Component to list users
export const Users = () => {
    const [isLoading, setIsLoading] = useState(true);
    const [users, setUsers] = useState([]);

    const dispatch = useDispatch();

    function onUsersFetchCompleted({ error, cancelled, data }) {
        setIsLoading(false);
        if (!err && !cancelled) {
            setUsers(data);
        }
    }

    useEffect(() => {
        dispatch({
            type: 'FETCH_USERS',
            onComplete: onUsersFetchCompleted,
        });
    }, []);

    return isLoading ? (
        'Loading'
    ) : (
        <ul>
            {users.map(user => (
                <li>{user.name}</li>
            ))}
        </ul>
    );
};

// Users.jsx

putWait

An effect that dispatches the action (same as put effect) which you can yield and wait for that saga to be completed only if the saga is created using withCallback higher order saga

Example

function* loadCurrentUserData() {
    const currentUserId = getCurrentUserId();

    let users = yield select(state => state.users);

    if(!users) {
        // waits until fetchUsers saga is completed
        // fetchUser saga is defined in userSaga.js above
        users = yield putWait({type: 'FETCH_USERS'});
    }

    return users.find(p => p.id === currentUserId);
}

export function*(){
    yield all([
        takeEvery('LOAD_CURRENT_USER', fetchUsers)
    ])
}

// userData.js