What is GraphQL Codegen: Overview and Usage

GraphQL Codegen is a tool that automatically generates code based on your GraphQL schema and queries. It helps developers create type-safe code and reduces manual work by producing ready-to-use code for queries, mutations, and types.

How It Works

Imagine you have a recipe book (your GraphQL schema) and you want to cook dishes (queries and mutations) without making mistakes. GraphQL Codegen acts like a smart assistant that reads your recipe book and writes down exact shopping lists and cooking steps (code) for you. This way, you don’t have to guess or write everything by hand.

It scans your GraphQL schema and the queries you write, then generates code in your preferred programming language. This code includes types, functions, and helpers that match your GraphQL setup perfectly. It saves time and prevents errors by ensuring your code always matches your GraphQL API.

Example

This example shows how to generate TypeScript types from a simple GraphQL query using GraphQL Codegen.

yaml

schema {
  query: Query
}

type Query {
  hello: String
}

# Query file: query.graphql
query SayHello {
  hello
}

# codegen.yml configuration
schema: ./schema.graphql
documents: ./query.graphql
generates:
  ./generated.ts:
    plugins:
      - typescript
      - typescript-operations

# Run command:
# graphql-codegen --config codegen.yml

Output

export type SayHelloQuery = {
  __typename?: 'Query';
  hello?: string | null;
};

When to Use

Use GraphQL Codegen when you want to avoid writing repetitive code for your GraphQL queries and mutations. It is especially helpful in projects where you want type safety, such as TypeScript or strongly typed languages, to catch errors early.

It is great for frontend apps that consume GraphQL APIs, backend services that call other GraphQL services, and any project where you want to keep your code in sync with your GraphQL schema automatically.

Key Points

• Automatically generates code from GraphQL schemas and queries.
• Supports many languages and frameworks like TypeScript, JavaScript, React, and more.
• Improves developer productivity by reducing manual coding.
• Ensures type safety and consistency with your GraphQL API.

Key Takeaways

GraphQL Codegen automates code creation from GraphQL schemas and queries.

It helps maintain type safety and reduces manual coding errors.

Ideal for projects using TypeScript or other typed languages.

Supports many languages and frameworks for flexible use.

Keeps your code synchronized with your GraphQL API changes.