GraphQL with Apollo Client vs TypeScript Type Inference: A Practical Comparison

Introduction

Modern web development increasingly relies on GraphQL for efficient data fetching and TypeScript for type safety. When using Apollo Client with TypeScript, developers can leverage GraphQL's schema and TypeScript's static typing to create robust applications. However, the interaction between GraphQL types and TypeScript type inference isn't always straightforward.

This post explores how Apollo Client and TypeScript type inference work together, comparing manual type definitions with automated tools like GraphQL Code Generator. We'll examine practical examples, trade-offs, and best practices for maintaining type safety in a GraphQL-powered TypeScript application.

Understanding GraphQL Types and TypeScript

GraphQL schemas define strict types for queries, mutations, and subscriptions. When using Apollo Client in a TypeScript project, these types must align with TypeScript's type system to ensure compile-time safety.

For example, consider a simple GraphQL query:

query GetUser($id: ID!) {  
  user(id: $id) {  
    id  
    name  
    email  
  }  
}

In TypeScript, we might manually define the corresponding types:

interface User {  
  id: string;  
  name: string;  
  email: string;  
}  

interface GetUserVariables {  
  id: string;  
}  

interface GetUserResponse {  
  user: User;  
}

While this works, maintaining these types manually becomes tedious as the schema evolves.

Apollo Client with Manual Type Definitions

Apollo Client allows explicit type annotations for queries and mutations using generics. Here's how you might use it with manual types:

import { useQuery, gql } from '@apollo/client';  

const GET_USER = gql`  
  query GetUser($id: ID!) {  
    user(id: $id) {  
      id  
      name  
      email  
    }  
  }  
`;  

function UserProfile({ userId }: { userId: string }) {  
  const { loading, error, data } = useQuery<GetUserResponse, GetUserVariables>(  
    GET_USER,  
    { variables: { id: userId } }  
  );  

  if (loading) return <p>Loading...</p>;  
  if (error) return <p>Error: {error.message}</p>;  

  return (  
    <div>  
      <h1>{data?.user.name}</h1>  
      <p>{data?.user.email}</p>  
    </div>  
  );  
}

Pros:

Full control over type definitions
No additional tooling required

Cons:

Manual maintenance becomes burdensome
Prone to drift from the actual GraphQL schema
No automatic updates when schema changes

Automating Type Safety with GraphQL Code Generator

GraphQL Code Generator is a popular tool that automatically generates TypeScript types from your GraphQL schema and operations. Here's how it works:

Define a configuration file (codegen.yml):

schema: http://localhost:4000/graphql  
documents: './src/**/*.graphql'  
generates:  
  ./src/generated/graphql.ts:  
    plugins:  
      - typescript  
      - typescript-operations  
      - typescript-react-apollo

Run the generator to produce TypeScript types.
Use the generated hooks in your components:

import { useGetUserQuery } from './generated/graphql';  

function UserProfile({ userId }: { userId: string }) {  
  const { loading, error, data } = useGetUserQuery({  
    variables: { id: userId },  
  });  

  // ... same rendering logic  
}

Advantages:

Always in sync with your GraphQL schema
Reduces boilerplate code
Provides complete type safety for all operations
Supports fragments, interfaces, and unions

Considerations:

Requires setup and build step
Generated types can be verbose

TypeScript Inference in Apollo Client 3

Apollo Client 3 introduced improved TypeScript support, including better type inference for cache operations. The TypedDocumentNode feature allows for even tighter integration:

import { TypedDocumentNode } from '@apollo/client';  

const GET_USER: TypedDocumentNode<GetUserResponse, GetUserVariables> = gql`  
  query GetUser($id: ID!) {  
    user(id: $id) {  
      id  
      name  
      email  
    }  
  }  
`;  

// Now useQuery infers types automatically  
const { data } = useQuery(GET_USER, { variables: { id: '1' } });  
// data is automatically typed as GetUserResponse | undefined

This approach provides excellent type safety while reducing manual annotation. When combined with GraphQL Code Generator, you can generate TypedDocumentNode definitions automatically.

Conclusion

Choosing between manual type definitions and automated tools for GraphQL and TypeScript integration depends on your project's scale and team preferences:

For small projects, manual type annotations with Apollo Client's generics might suffice.
For medium to large projects, GraphQL Code Generator dramatically improves maintainability.
Apollo Client 3's enhanced type inference offers a good middle ground, especially when combined with TypedDocumentNode.

The ideal approach often involves using GraphQL Code Generator for type generation while leveraging Apollo Client's built-in type inference capabilities. This combination provides the strongest type safety with minimal maintenance overhead, ensuring your GraphQL operations remain type-safe as your schema evolves.

By understanding these different approaches, teams can make informed decisions about their GraphQL and TypeScript integration strategy, balancing type safety with developer productivity.

GraphQL with Apollo client vs TypeScript type inference