Fetching Data with Get Requests using Fetch in React Native

In this tutorial, we'll learn how to fetch data by sending GET requets using Fetch in React Native.

Instead of waiting one second in vein, let’s fetch data and wait for it before we display the home screen.

We’ll be using the news API from NewsAPI.org, register for an account and you’ll get an API key, note it and let’s continue.

React Native provides the Fetch API for fetching data from remote servers and APIs. It’s quite similar to the browser APIs such as fetch() and XMLHttpRequest.

The API is promise-based, so you can also use it with the async/await syntax.

Note: React Native supports the XMLHttpRequest API; so that means you can also use libraries like Axios (after you install it) to fetch data and send API requests.

For more information about Fetch, see Networking on the official docs.

Now, let’s fetch our data.

First, import the useEffect() hook:

import React, { useState, useEffect } from 'react';

useEffect is a builtin hook that allows you to perform side effects in your React application such as fetching data.

Next, inside the App() function, add the API_KEY and URL variables:

const App = () => {
  const API_KEY = "<YOUR_API_KEY_HERE>";
  const URL = `https://newsapi.org/v2/top-headlines?sources=techcrunch&apiKey=${API_KEY}`;

Note: Don’t forget to change <YOUR_API_KEY_HERE> with your actual API key.

Next, add the articles array for holding the fetched articles:

  const [articles, setArticles] = useState([]);

Next, call the fetch() method inside the useEffect() hook to fetch data from the API:

  useEffect(()=>{
    fetch(URL)
    .then((response) => response.json())
    .then((responseJson) => {
      return responseJson.articles;
    })
    .then( articles  => {
      setArticles(articles);
      setLoading(false);
    })
    .catch( error => {
      console.error(error);
    });

  } , []);

Once data is fetched, we assign it to the articles variable and we set the loading variable to false.

Also, pass the articles state to the <HomeScreen> component via an articles prop:

  if (loading){
      return <SplashScreen />
    } else {
      return <HomeScreen articles = { articles }/>
  }

This is the complete source code of the function:

const App = () => {
  const API_KEY = "<YOUR_API_KEY_HERE>";
  const URL = `https://newsapi.org/v2/top-headlines?sources=techcrunch&apiKey=${API_KEY}`;
  const [articles, setArticles] = useState([]);
  const [loading, setLoading ] = useState(true);
  useEffect(()=>{
    fetch(URL)
    .then((response) => response.json())
    .then((responseJson) => {
      return responseJson.articles;
    })
    .then( articles  => {
      setArticles(articles);
      //console.log(articles);
      setLoading(false);
    })
    .catch( error => {
      console.error(error);
    });

  } , []);

  if (loading){
      return <SplashScreen />
    } else {
      return <HomeScreen articles = { articles }/>
  }
};

Now, we need to change the <HomeScreen> component to display the data passed as a prop:

const HomeScreen = (props) => {
  console.log("articles: ", props.articles);
  return (
    <View>
      {
        props.articles.map((article, index)=>{
          return <Text key = {index}>
          { article.title }
          </Text>
        })
      }
    </View>
  );
}

We loop through the articles prop using the JavaScript map() method and we use a <Text> component to display the title of each article.

This not the best way to display lists of data. In the next section, we’ll see how to use the FlatList component.

Note: You may notice the use of console.log() in our code to display some information for debugging. In React Native, you need to open a new terminal and run the react-native log-android command if you want to see the output of console.log(). This is based on logkitty.

• Date: 09 Aug 2019