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Adding Relay

Introduction to Relay​

Relay is a powerful GraphQL client framework developed by Facebook. It allows you to efficiently fetch and manage data from a GraphQL server in your React applications. Relay optimizes data fetching by batching and coalescing requests, reducing over-fetching and making your app more performant.

Prerequisites​

Before we begin, make sure you have the following installed:

  1. Node.js and npm (Node Package Manager) - You can download it from the official website: https://nodejs.org/

  2. Create React App - You can create a new React application using Create React App with the following command in your terminal:

    npx create-react-app my-relay-app
    cd my-relay-app

  3. Basic knowledge of React and GraphQL will be helpful, but we'll try to explain everything in a beginner-friendly way.

Adding Relay to Your Create React App​

Let's integrate Relay into your Create React App project.

Step 1: Install Dependencies​

Open your terminal, navigate to your project directory, and install the necessary packages:

npm install relay react-relay

Step 2: Setup Relay Environment​

Relay requires a network layer to communicate with your GraphQL server. For this example, we'll use the GitHub GraphQL API. Open your src folder and create a new file named relay-environment.js:

src/relay-environment.js

import { Environment, Network, RecordSource, Store } from 'relay-runtime';

async function fetchGraphQL(operation, variables) {
  const response = await fetch('https://api.github.com/graphql', {
    method: 'POST',
    headers: {
      Authorization: 'Bearer YOUR_GITHUB_ACCESS_TOKEN', // Replace with your GitHub access token
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      query: operation.text,
      variables,
    }),
  });
  return await response.json();
}

const environment = new Environment({
  network: Network.create(fetchGraphQL),
  store: new Store(new RecordSource()),
});
export default environment;

Replace YOUR_GITHUB_ACCESS_TOKEN with a valid GitHub Personal Access Token. You can create one by following the steps in this guide: https://docs.github.com/en/authentication/creating-a-personal-access-token.

Step 3: Update index.js​

Now, let's make sure our app uses the Relay environment. Open src/index.js and update it as follows:

src/index.js

import React from 'react';
import ReactDOM from 'react-dom';
import { RelayEnvironmentProvider } from 'react-relay';
import environment from './relay-environment';
import App from './App';

ReactDOM.render(
  <RelayEnvironmentProvider environment={environment}>
    <App />
  </RelayEnvironmentProvider>,
  document.getElementById('root')
);

Step 4: Writing Your First Relay Query​

In this example, we'll fetch a user's details from the GitHub API using Relay. Create a new file named User.js inside the src folder:


import React from 'react';
import { graphql, useFragment } from 'react-relay';

const userFragment = graphql`
  fragment User_user on User {
    name
    login
    avatarUrl
  }
`;

function User(props) {
  const user = useFragment(userFragment, props.user);
  return (
    <div>
      <img src={user.avatarUrl} alt={user.name} />
      <h2>{user.name}</h2>
      <p>{user.login}</p>
    </div>
  );
}

export default User;

Step 5: Create a Relay Query Component​

Now, let's create a component that uses the User component and fetches the data using Relay. Create a new file named Profile.js inside the src folder:

src/Profile.js

import React from 'react';
import { graphql, useLazyLoadQuery } from 'react-relay';

const profileQuery = graphql`
  query ProfileQuery {
    viewer {
      ...User_user
    }
  }
`;

function Profile() {
  const data = useLazyLoadQuery(profileQuery, {});
  return <User user={data.viewer} />;
}

export default Profile;

Step 6: Add Routing (Optional)​

To view the user profile, we'll add routing to your app using react-router-dom. First, install the package:

npm install react-router-dom

Then, update src/App.js:

src/App.js

import React from 'react';
import { BrowserRouter as Router, Route, Switch, Link } from 'react-router-dom';
import Profile from './Profile';

function App() {
  return (
    <Router>
      <div>
        <nav>
          <ul>
            <li>
              <Link to="/">Home</Link>
            </li>
            <li>
              <Link to="/profile">Profile</Link>
            </li>
          </ul>
        </nav>

        <Switch>
          <Route path="/profile">
            <Profile />
          </Route>
          <Route path="/">
            <h1>Welcome to My Relay App</h1>
          </Route>
        </Switch>
      </div>
    </Router>
  );
}

export default App;

Step 7: Start Your App​

Now, you're all set! Save your changes and start your app:

npm start

Visit http://localhost:3000/profile to see your Relay-powered user profile page!

Conclusion​

Congratulations! You've successfully integrated Relay into your Create React App and fetched data from the GitHub API. This is just the beginning of what Relay can do for your React applications. Continue exploring Relay's documentation and its powerful features to take your app to the next level.

Info

Remember to replace the GitHub API with your own GraphQL API to experiment further with Relay. Happy coding!