Migration from REST to GraphQL - Mini Project: Build & Apply

Migration from REST to GraphQL

📖 Scenario: You work for a company that currently uses REST APIs to fetch user data. The company wants to switch to GraphQL to make data fetching more flexible and efficient.You will build a simple GraphQL schema and resolver setup that mimics the existing REST data structure.

🎯 Goal: Create a GraphQL schema and resolver that fetch user information similar to the existing REST API response.Learn how to define types, queries, and resolve data in GraphQL.

📋 What You'll Learn

Define a GraphQL type User with fields id, name, and email

Create a query type Query with a field users that returns a list of User

Set up a resolver for users that returns the exact user data

Add a configuration variable maxUsers to limit the number of users returned

💡 Why This Matters

🌍 Real World

Many companies migrate from REST APIs to GraphQL to improve data fetching efficiency and flexibility in their applications.

💼 Career

Understanding how to define GraphQL schemas and resolvers is essential for backend developers working with modern API technologies.

1

Define the User type and sample data

Create a GraphQL type called User with fields id (ID!), name (String!), and email (String!). Also, create a constant userData as an array of three user objects with these exact values: {id: "1", name: "Alice", email: "[e-mail]"}, {id: "2", name: "Bob", email: "[e-mail]"}, {id: "3", name: "Charlie", email: "[e-mail]"}.

GraphQL

# Define the User type and userData array
# Your code here

Need a hint?

Use gql`...` to define the GraphQL type. Create userData as an array of objects with exact fields and values.

2

Add Query type and maxUsers configuration

Add a Query type to the schema with a field users that returns a list of User. Also, create a constant maxUsers and set it to 2 to limit the number of users returned.

GraphQL

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

const typeDefs = gql`
  type User {
    id: ID!
    name: String!
    email: String!
  }

  # Add Query type here
`;

const userData = [
  { id: "1", name: "Alice", email: "[e-mail]" },
  { id: "2", name: "Bob", email: "[e-mail]" },
  { id: "3", name: "Charlie", email: "[e-mail]" }
];

# Define maxUsers constant here

Need a hint?

Add the Query type inside the gql template. Define maxUsers as a constant number.

3

Create resolver for users query with limit

Create a resolvers object with a Query field. Inside Query, define a users function that returns the first maxUsers entries from userData using slice(0, maxUsers).

GraphQL

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

const typeDefs = gql`
  type User {
    id: ID!
    name: String!
    email: String!
  }

  type Query {
    users: [User]
  }
`;

const userData = [
  { id: "1", name: "Alice", email: "[e-mail]" },
  { id: "2", name: "Bob", email: "[e-mail]" },
  { id: "3", name: "Charlie", email: "[e-mail]" }
];

const maxUsers = 2;

# Create resolvers object with Query.users resolver here

Need a hint?

Define resolvers as an object with a Query field. The users function returns a slice of userData.

4

Export schema and resolvers for server setup

Export typeDefs and resolvers using module.exports so they can be used in the GraphQL server setup.

GraphQL

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

const typeDefs = gql`
  type User {
    id: ID!
    name: String!
    email: String!
  }

  type Query {
    users: [User]
  }
`;

const userData = [
  { id: "1", name: "Alice", email: "[e-mail]" },
  { id: "2", name: "Bob", email: "[e-mail]" },
  { id: "3", name: "Charlie", email: "[e-mail]" }
];

const maxUsers = 2;

const resolvers = {
  Query: {
    users: () => userData.slice(0, maxUsers)
  }
};

# Export typeDefs and resolvers here

Need a hint?

Use module.exports to export both typeDefs and resolvers.