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!