Redux Saga Fetch API - Javascript

Redux Saga is a popular middleware library for Redux, which provides an alternative approach to manage side effects in your application. In comparison to Redux Thunk, Redux Saga offers more advanced features, such as complex or long-running asynchronous operations, error handling, and more. In this article, we will explore how to use Redux Saga to fetch API data from your backend.

Setting up Redux Saga and the Fetch API

To get started, you need to install both Redux Saga and the Fetch API. You can do this by running the following command in your terminal:

npm install redux-saga isomorphic-fetch

Then, you need to configure Redux Saga to handle the side effects in your application by creating a saga middleware and integrating it into your Redux store. Here is an example of how you can do this:

import { createStore, applyMiddleware } from 'redux';
import createSagaMiddleware from 'redux-saga';
import rootReducer from './reducers';
import { fetchPostsSaga } from './sagas';

const sagaMiddleware = createSagaMiddleware();

const middleware = [sagaMiddleware];

const store = createStore(
  rootReducer,
  applyMiddleware(...middleware)
);

sagaMiddleware.run(fetchPostsSaga);

export default store;

In this example, we create a createSagaMiddleware function from Redux Saga and integrate it with the Redux store using the applyMiddleware function. Then, we create a saga called fetchPostsSaga that we will use to fetch API data.

Fetching API Data using Redux Saga

Once you have your Redux Saga middleware and store set up, you can start fetching API data by creating a generator function that describes the asynchronous logic of your saga. This function is known as a saga worker.

Here is an example of how you can create a saga worker that uses the Fetch API to retrieve data from a server:

import { call, put, takeLatest } from 'redux-saga/effects';
import fetch from 'isomorphic-fetch';

function* fetchPosts() {
  try {
    const response = yield call(fetch, 'https://jsonplaceholder.typicode.com/posts');
    const data = yield response.json();
    yield put({ type: 'RECEIVE_POSTS_SUCCESS', payload: data });
  } catch (err) {
    yield put({ type: 'RECEIVE_POSTS_FAILURE', payload: err.message });
  }
}

export function* fetchPostsSaga() {
  yield takeLatest('FETCH_POSTS_REQUEST', fetchPosts);
}

In this example, we create a saga worker called fetchPosts that uses the call, put, and takeLatest effects from Redux Saga. When the FETCH_POSTS_REQUEST action is dispatched, the takeLatest effect waits for the previous request to complete before starting a new one.

The call effect invokes the fetch function with a URL string that returns a Promise. The yield keyword is used to pause the execution of the generator function until the Promise is resolved.

Once the response is received, the data is extracted from the response using the json method and then dispatched to the Redux store using the put effect with the RECEIVE_POSTS_SUCCESS action and the payload.

If an error occurs during the fetch request, the catch block catches the error, dispatches a RECEIVE_POSTS_FAILURE action with an error message payload.

Using the Saga Worker in your Application

Once you have created your Saga worker function, you need to call it from your application. To do this, you will dispatch an action that triggers the saga worker function. Here is an example of how you can do this:

dispatch({ type: 'FETCH_POSTS_REQUEST' });

In this example, we dispatch an action with the FETCH_POSTS_REQUEST type that triggers the fetchPosts saga worker.

Conclusion

In conclusion, Redux Saga provides a powerful way to manage side effects like fetching API data in your Redux application. By using the call, put, and other effects, you can describe complex asynchronous operations that make your application more robust and maintainable. In addition, the Fetch API provides a simple way to make HTTP requests that work in both browser and Node.js environments.