redux-saga module example

actions.js

// redux/user/actions.js
import * as types from './types';

export function fetchUserRequest(userId){
  return {
    type: types.FETCH_USER_REQUEST,
    payload: userId
  }
}

export function fetchUserSuccess(user){
  return {
    type: types.FETCH_USER_SUCCESS,
    payload: user
  }
}

export function fetchUserFailure(error){
  return {
    type: types.FETCH_USER_FAILURE,
    payload: error
  }
}

reducer.js

// redux/user/reducer.js
import * as types from './types';

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

export default function(state = initialState, { type, payload }) {
  switch (type) {
    case types.FETCH_USER_REQUEST:
      return {
        ...state,
        loading: true,
      };

    case types.FETCH_USER_SUCCESS:
      return {
        ...state,
        ...payload,
        loading: false,
      };

    case types.FETCH_USER_FAILURE:
      return {
        ...state,
        loading: false,
        error: {
          ...payload,
        },
      };
      
    default:
      return state;
  }
}

Redux-saga module example.md

Gist contains example files for redux-saga user(GET) module. The structure of redux for included files in this gist:

redux
├── user                          # Module name
│   ├── __tests__                 # Directory for redux module tests
│   │   ├── actions.test.js       # Action tests
│   │   └── saga.test.js          # Saga tests
│   ├── actions.js                # Module actions (f/e.: fetchUserRequest, fetchUserSuccess)
│   ├── reducer.js                # Module reducer
│   ├── saga.js                   # Module saga
│   └── types.js                  # Declared module constants (f/e.: FETCH_USER_REQUEST)

Example of redux with nested module

redux
├── user                          # Module name
│   ├── add                       # Sub-module name
│   │   ├── __tests__
│   │   │   ├── actions.test.js
│   │   │   └── saga.test.js
│   │   ├── actions.js
│   │   ├── reducer.js
│   │   ├── saga.js
│   │   └── types.js
│   └── delete
│       ├── __tests__
│       │   ├── actions.test.js
│       │   └── saga.test.js
│       ├── actions.js
│       ├── reducer.js
│       ├── saga.js
│       └── types.js
|
├── user-cats
│   ├── __tests__
│   │   ├── actions.test.js
│   │   └── saga.test.js
│   ├── actions.js
│   ├── reducer.js
│   ├── saga.js
│   └── types.js
|
├── root-reducer.js             # Reducers from ALL modules are here
└── root-saga.js                # Sagas from ALL modules are here

root-reducer.js

// redux/root-reducer.js
import { combineReducers } from 'redux';

import user from './user/reducer';
import userCats from './user-cats/reducer';

const rootReducer = combineReducers({
  user,
  userCats,
});

export default rootReducer;

root-saga.js

// redux/root-saga.js
import {all} from 'redux-saga/effects';
import { watchUser } from './user/saga';
import { watchUserCats } from './user-cats/saga';

export default function* rootSaga() {
  yield all([
    watchUser(),
    watchUserCats(),
  ]);
}

saga.js

// redux/user/saga.js
import {call, put, push, takeEvery} from 'redux-saga/effects';
import { setLocalstorage } from 'utils/localstore';
import { toast } from 'utils/toast';
import { routes } from 'routes';
import * as types from './types';
import * as actions from './actions';

export function* fetchUserSaga({ payload }) {
  const { user, error } = yield call(api.fetchUser, payload);
  
  if(error){
    yield put(actions.fetchUserFailure(error));
    yield call(toast, "error", error); // show error toast
  } else {
    yield put(actions.fetchUserSuccess(user));
    yield call(toast, "success"); // show success toast
    // yield push(routes.DASHBOARD); // if necessary redirect via push action provided by redux-saga
    yield call(setLocalstorage, "userData", user); // save to localStorage
  }
}

export function* watchUser() {
  yield takeEvery(types.FETCH_USER_REQUEST, fetchUserSaga)
}

saga.test.js

// redux/user/__tests__/saga.test.js
import {call, put, push, takeEvery} from 'redux-saga/effects';
import { setLocalstorage } from 'utils/localstore';
import { toast } from 'utils/toast';
import { routes } from 'routes';
import { fetchUserSaga, fetchUser } from '../saga';
import * as actions from '../actions';

describe('User saga', () => {
  describe('Fetch user', () => {
    const payload = {
      username: 'Bob',
    };
    
    describe('when success', () => {
      test('should dispatch success action', () => {
        const saga = fetchUserSaga({ payload });
        const response = { 
          username: 'Bob',
        };

        expect(saga.next().value).toEqual(call(fetchUser, payload));
        expect(saga.next(response).value).toEqual(put(actions.fetchUserSuccess(response)));
      });
      
      test('should show success toast notification', () => {
        const saga = fetchUserSaga({ payload });
        const response = { 
          username: 'Bob',
        };

        expect(saga.next().value).toEqual(call(fetchUser, payload));
        expect(saga.next(response).value).toEqual(put(actions.fetchUserSuccess(response)));
        expect(saga.next().value).toEqual(call(toast, 'success'));
      });
    });

    describe('when error', () =>{
      test('should dispatch an error action', () =>{
        const saga = fetchUserSaga({ payload });
        const response = { error: {message: 'fake err'}};

        expect(saga.next().value).toEqual(call(fetchUser, payload));
        expect(saga.next(response).value).toEqual(put(actions.fetchUserFailure(response.error.message)))
      })
    });
  })
});

types.js

// redux/user/types.js
export const FETCH_USER_REQUEST = 'FETCH_USER_REQUEST';
export const FETCH_USER_SUCCESS = 'FETCH_USER_SUCCESS';
export const FETCH_USER_FAILURE = 'FETCH_USER_FAILURE';

Is a good pattern use toast's inside a saga?

Personally didn't find any better solution back then.
Didn't touch redux-saga in a while so perhaps there is a better solution existing nowadays.