1 Jul 2020

Generating TypeScript types and React Hooks based on GraphQL endpoint.

Autogenerate Typescript types and custom React Hooks with GraphQL Code Generator in React applications.

Typescript illustration cover.

Nowadays, developing ReactJS with TypeScript gives us a solid way to write applications: it adds the advantage of type safety, component auto-documentation, error handling, and accurate autocomplete in the editor code. However, writing types and keeping them maintainable still requires considerable effort. Moreover, when the data provider is a GraphQL server, it makes you feel like you're doing a useless job, given the server already has its own schemas for types. Seems redundant, right?

With this in mind, GraphQL Code Generator allows us to generate TypesScript typing out of GraphQL schemas. Beyond that, it gives us a couple of plugins to create custom React hooks that don't require any kind of maintenance or workaround to fit into your application.

Among many others, some of the benefits of using this tool:

  • Codeless: forget about creating the interfaces/types for every GraphQL endpoint; save time and spend effort on what matters.

  • Development experience: as a result of having the types always available, your editor will provide meaningful, autocomplete and error checking.

  • Types always up-to-date: if your GraphQL endpoint schemas change, your application will be updated, and Typescript will help you make sure you make the necessary changes.


First of all, let's install the dependencies needed:

npm i @apollo/react-hooks graphql
npm i @graphql-codegen/cli @graphql-codegen/import-types-preset @graphql-codegen/typescript @graphql-codegen/typescript-operations @graphql-codegen/typescript-react-apollo --save-dev

I'm considering the following folder structure, but of course, feel free to adapt it to your liking. Just keep in mind that it needs a place to store the schemas that will be fetched by the Code Generator:

📦 my-project
 ┣ 📂 src
 ┃ ┣ 📂 pages
 ┃ ┃ ┗ index.tsx
 ┃ ┣ 📂 queries
 ┃ ┃ ┣ 📂 autogenerate
 ┃ ┃ ┗ my-query.gql
 ┃ ┗ apollo-client.ts
 ┣ codegen.yml
 ┗ package.json

Then, you'll need to create a configuration file at the root of the project, named codegen.yml. The following snippet shows how I usually set it up in my projects, where it generates different files for its own purpose – in other words, split by concerns like GraphQL operations and server schemas:

# Endpoint API, the following URL is a example
schema: https://countries-274616.ew.r.appspot.com/graphql/
overwrite: true

# Format files
    - prettier --write

  # Get schemas from server
    documents: 'src/queries/**/**.gql'
      - typescript

  # Create operations based on queries 
    documents: 'src/queries/**/**.gql'
    preset: import-types
      typesPath: ./schemas
      - typescript-operations

  # 1. Export GraphQL documents 
  # 2. React interface
    documents: 'src/queries/**/**.gql'
    preset: import-types
      typesPath: ./operations
      - typescript-react-apollo
      # Optionals
      withHOC: false
      withComponent: false
      withHooks: true

Also, let's add the scripts to generate the schemas and watch the files change in package.json:

"scripts": {
  "schemas": "graphql-codegen --config codegen.yml",
  "schemas:watch": "npm run schemas -- --watch",

And as it turns out in the editor code:

Typescript editor code.

This is only one of the possible ways to use it, since it has many plugins, presets, integrations, and configurations for different purposes such as generating React higher-order components, Gatsby integration, prettier and lint the files, among other cool things. Feel free to check out the documentation here.

I've made a repository available with the code above, and you can check it out here.

Danilo Woznica

(Former) Lead Front-end Developer

Author page

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