Building GraphQL APIs with Angular

GraphQL is a query language for APIs that allows clients to request only the data they need. This lesson will guide you through building a GraphQL API using Angular, covering essential concepts and practical implementation steps.

GraphQL enables developers to define the structure of the data required and provides a more efficient way to interact with APIs compared to REST.

Key Concepts:

• **Queries**: Used to fetch data.
• **Mutations**: Used to modify data.
• **Subscriptions**: Used for real-time updates.

To start building a GraphQL API with Angular, ensure you have Angular CLI installed. Create a new Angular application by running:

ng new graphql-angular-app

Navigate into your project directory:

cd graphql-angular-app

For this example, we will use Apollo Server to create a simple GraphQL API.

Step-by-Step Process:

1. Install Apollo Server and GraphQL:

npm install apollo-server graphql

2. Create a new file server.js:

const { ApolloServer, gql } = require('apollo-server');

const typeDefs = gql` 
  type Query { 
    hello: String 
  } 
`;

const resolvers = { 
  Query: { 
    hello: () => 'Hello world!' 
  } 
};

const server = new ApolloServer({ typeDefs, resolvers });

server.listen().then(({ url }) => { 
  console.log(`🚀 Server ready at ${url}`); 
});
                

3. Run your server:

node server.js

To connect your Angular app with the GraphQL API, you can use Apollo Angular.

Installation:

ng add apollo-angular

Service Setup:

import { Injectable } from '@angular/core';
import { Apollo, gql } from 'apollo-angular';

@Injectable({
  providedIn: 'root'
})
export class GraphQLService {
  constructor(private apollo: Apollo) {}

  getHello() {
    return this.apollo.query({
      query: gql` 
        query { 
          hello 
        } 
      `
    });
  }
}
            

• Use descriptive names for queries and mutations.
• Implement pagination for large datasets.
• Utilize caching mechanisms for better performance.