API Development and Integration

Chapter 10: GraphQL Introduction

10.1 GraphQL Basics

GraphQL is a query language for APIs that allows clients to request exactly the data they need.

// GraphQL schema
const { buildSchema } = require('graphql');

const schema = buildSchema(`
    type User {
        id: ID!
        name: String!
        email: String!
        posts: [Post!]!
    }
    
    type Post {
        id: ID!
        title: String!
        content: String!
        author: User!
    }
    
    type Query {
        user(id: ID!): User
        users: [User!]!
    }
    
    type Mutation {
        createUser(name: String!, email: String!): User!
    }
`);

10.2 GraphQL Queries

// Client query
query {
    user(id: "1") {
        name
        email
        posts {
            title
            content
        }
    }
}

// Resolver implementation
const root = {
    user: async ({ id }) => {
        return await User.findById(id);
    },
    users: async () => {
        return await User.findAll();
    }
};

10.3 GraphQL vs REST

GraphQL Advantages:

• Fetch only needed data
• Single endpoint
• Strong typing
• Real-time subscriptions

REST Advantages:

• Simpler for simple use cases
• Better caching
• More mature ecosystem
• Easier to understand