This course path teaches Apollo Server 3, which has been deprecated. To access the new course paths covering Apollo Server 4, use this course path.

In this lesson, we will define basic types and write simple queries in GraphQL using Apollo Server. By the end, you'll create a basic GraphQL server to fetch a list of books, building on what you've learned about setting up a GraphQL server.

We'll start by setting up a new Apollo Server instance to manage our GraphQL server. Let's do it step-by-step.

1. Define the GraphQL schema:

   TypeScript
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   1import { ApolloServer, gql } from 'apollo-server';
   2
   3const typeDefs = gql`
   4  type Book {
   5    title: String
   6    author: String
   7  }
   8
   9  type Query {
   10    books: [Book]
   11  }
   12`;

   In this schema:

   • The Book type has title and author fields, both of which are strings.
   • The Query type includes a books field that returns an array of Book objects.

2. Create sample data:

   TypeScript
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   1const books = [
   2  { title: 'The Hobbit', author: 'J.R.R. Tolkien' },
   3  { title: 'Harry Potter', author: 'J.K. Rowling' },
   4];

   This array will act as our in-memory database of books.

3. Define resolvers:

   TypeScript
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   1const resolvers = {
   2  Query: {
   3    books: () => books,
   4  },
   5};

   Here, the resolver for the books query simply returns the books array we defined earlier.

4. Initialize, configure, and start Apollo Server:

   TypeScript
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   1const server = new ApolloServer({ typeDefs, resolvers });
   2server.listen().then(({ url }) => {
   3  console.log(`🚀 Server ready at ${url}`);
   4});

   Running this command will start the server and print the URL where it's accessible.

With the server running, let's write and execute a query to fetch the list of books.

TypeScript
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1import fetch from 'node-fetch';
2
3const query = `
4  query {
5    books {
6      title
7      author
8    }
9  }
10`;
11
12const url = 'http://localhost:4000/';
13
14fetch(url, {
15  method: 'POST',
16  headers: {
17    'Content-Type': 'application/json',
18  },
19  body: JSON.stringify({ query }),
20})
21  .then((response) => response.json())
22  .then((data) => console.log(JSON.stringify(data, null, 2)))
23  .catch((error) => console.error('Error:', error));

This script:

• Sends a POST request to the server with a query to fetch books.
• Logs the response, which should include the list of books with their titles and authors.

The script outputs:

JSON
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1{
2  "data": {
3    "books": [
4      {
5        "title": "The Hobbit",
6        "author": "J.R.R. Tolkien"
7      },
8      {
9        "title": "Harry Potter",
10        "author": "J.K. Rowling"
11      }
12    ]
13  }
14}

This output confirms that our server correctly handles the query and returns the expected data.

In this lesson, we:

• Created a schema with a basic type (Book).
• Set up resolvers to fetch data.
• Wrote and ran queries to retrieve a list of books.

Next, you will practice what you've learned by tackling exercises that help solidify these concepts. The following lessons will cover more complex queries and mutations.

Happy coding!