This content originally appeared on DEV Community and was authored by Kauna Hassan
GraphQL is an API query language that allows for more flexible data requests. It enables you to request only what you require, reducing the amount of data transferred over the network significantly. Furthermore, GraphQL includes a type system for query validation, making it easier to maintain and evolve APIs over time. This article will go over how to use GraphQL with React, including how to set up a GraphQL server, write queries, and cache data.
Setting up a GraphQL server
To get started with GraphQL, we must first create a GraphQL server. There are numerous approaches, but we will use Apollo Server, a popular open-source GraphQL server that can be used with a wide range of languages and frameworks.
Run the following command to install Apollo Server:
npm install apollo-server
Following that, we can build a basic GraphQL server by specifying a schema and resolvers. The schema defines the types that can be queried and their fields, whereas the resolvers implement the queries.
Here's an example of a schema:
type Query {
hello: String
}
And an example of a resolver
const resolvers = {
Query: {
hello: () => 'Hello world!'
}
};
Then we can launch an Apollo Server instance and begin listening for requests:
const { ApolloServer } = require('apollo-server');
const server = new ApolloServer({ typeDefs, resolvers });
server.listen().then(({ url }) => {
console.log(`Server ready at ${url}`);
});
Writing queries
Now that we've set up a GraphQL server, we can start writing queries to get data from it. To send queries and receive data in React, we can use the Apollo Client library.
Run the following command to install Apollo Client:
npm install @apollo/client
Then we can make a client instance and use the useQuery hook to send a query and receive data:
import { ApolloClient, InMemoryCache, gql, useQuery } from '@apollo/client';
const client = new ApolloClient({
uri: 'http://localhost:4000',
cache: new InMemoryCache()
});
const GET_HELLO = gql`
query {
hello
}
`;
function Hello() {
const { loading, error, data } = useQuery(GET_HELLO);
if (loading) return <p>Loading...</p>;
if (error) return <p>Error :(</p>;
return <p>{data.hello}</p>;
}
This example queries the GraphQL server and displays the response. When the data changes, the useQuery hook automatically fetches it and updates the UI.
Data caching
One of the advantages of using Apollo Client is that it includes a cache for storing and reusing data. This can significantly improve performance while also reducing network traffic.
To demonstrate caching, let's modify the previous example to fetch the hello query twice:
function HelloTwice() {
const { loading, error, data } = useQuery(GET_HELLO, { fetchPolicy: 'cache-and-network' });
if (loading) return <p>Loading...</p>;
if (error) return <p>Error :(</p>;
return (
<div>
<p>{data.hello}</p>
<p>{data.hello}</p>
</div>
);
}
We set the fetchPolicy option to "cache-and-network", which instructs Apollo Client to first try to fetch the data from the cache, and if that fails or the data is stale, to fetch it from the network. We can avoid an unnecessary network request if the data is already in the cache.
Conclusion
We looked at how to use GraphQL with React, including how to set up a GraphQL server, write queries, and cache data. GraphQL provides a powerful way to build UIs that can consume that data, while React provides a flexible and efficient way to request data. By combining these two technologies, we can create robust and performant web applications that can scale with our needs.
If you want to learn more about GraphQL and React, I recommend reading the Apollo documentation, which includes step-by-step instructions and examples for using the Apollo Client and Apollo Server. Have fun coding!
This content originally appeared on DEV Community and was authored by Kauna Hassan
Kauna Hassan | Sciencx (2023-02-25T15:15:17+00:00) Implementing GraphQL in React Applications. Retrieved from https://www.scien.cx/2023/02/25/implementing-graphql-in-react-applications/
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