Create GraphQL schema and resolvers with TypeScript, using classes and decorators!
https://19majkel94.github.io/type-graphql/
We all know that GraphQL is so great and solves many problems that we have with REST API, like overfetching and underfetching. But developing a GraphQL API in Node.js with TypeScript is sometimes a bit of pain. Why? Let's take a look at the steps we usually have to make.
At first, we create the all the schema types in SDL. We also create our data models using ORM classes, which represents our db entities. Then we start to write resolvers for our queries, mutations and fields, but this forces us to first create TS interfaces for all arguments, inputs, and even object types. Only then can we actually implement the resolvers, using weird generic signatures, e.g.:
export const recipesResolver: GraphQLFieldResolver<void, Context, RecipesArgs> =
async (_, args) => {
// our business logic, e.g.:
const repository = getRepository(Recipe);
return repository.find();
}The biggest problem is the redundancy in our codebase, which makes it difficult to keep things in sync. To add a new field to our entity, we have to jump through all the files - modify an entity class, the schema, as well as the interface. The same goes with inputs or arguments. It's easy to forget to update one piece or make a mistake with a single type. Also, what if we've made a typo in field name? The rename feature (F2) won't work correctly.
TypeGraphQL comes to address this issues, based on experience from over a dozen months of developing GraphQL APIs in TypeScript. The main idea is to have only one source of truth by defining the schema using classes and a bit of decorator help. Additional features like dependency injection, validation or auth guards helps with common tasks that normally we would have to handle by ourselves.
As I mentioned, TypeGraphQL makes developing a GraphQL API and enjoyable process, i.e. by defining the schema using only classes and a bit of decorator magic.
So, to create types like object type or input type, we use kind of DTO classes.
For example, to declare Recipe type we simply create a class and annotate it with decorators:
@ObjectType()
class Recipe {
@Field(type => ID)
id: string;
@Field()
title: string;
@Field(type => [Rate])
ratings: Rate[];
@Field({ nullable: true })
averageRating?: number;
}And we get corresponding part of schema in SDL:
type Recipe {
id: ID!
title: String!
ratings: [Rate!]!
averageRating: Float
}Then we can create queries, mutations and field resolvers. For this purpose we use controller-like classes that are called "resolvers" by convention. We can also use awesome features like dependency injection or auth guards:
@Resolver(Recipe)
class RecipeResolver {
constructor(
private recipeService: RecipeService,
) {}
@Query(returns => [Recipe])
recipes() {
return this.recipeService.findAll();
}
@Mutation()
@Authorized(Roles.Admin)
removeRecipe(@Arg("id") id: string): boolean {
return this.recipeService.removeById(id);
}
@FieldResolver()
averageRating(@Root() recipe: Recipe) {
return recipe.ratings.reduce((a, b) => a + b, 0) / recipe.ratings.length;
}
}And in this simple way we get this part of schema in SDL:
type Query {
recipes: [Recipe!]!
}
type Mutation {
removeRecipe(id: String!): Boolean!
}Full getting started guide with a simple walkthrough/tutorial can be found in getting started docs.
The documentation with detailed description of the API and the features is available on the website.
Below you can find installation instructions that are also important.
- Install module:
npm i type-graphql
reflect-metadatashim is required:
npm i reflect-metadata
and make sure to import it on top of your entry file (before you use/import type-graphql or your resolvers):
import "reflect-metadata";- Its important to set these options in
tsconfig.jsonfile of your project:
{
"emitDecoratorMetadata": true,
"experimentalDecorators": true
}TypeGraphQLis designed to work with Node.js 6, 8 and latest stable. It uses features from ES7 (ES2016) so you should set yourtsconfig.jsonappropriately:
{
"target": "es2016" // or newer if your node.js version supports this
}- Due to using
graphql-subscriptiondependency that rely on anAsyncIterator, you may also have to provide theesnext.asynciterableto theliboption:
{
"lib": ["es2016", "esnext.asynciterable"]
}All in all, the minimal tsconfig.json file example looks like this:
{
"compilerOptions": {
"target": "es2016",
"module": "commonjs",
"lib": ["es2016", "esnext.asynciterable"],
"experimentalDecorators": true,
"emitDecoratorMetadata": true
}
}You can also check the examples folder on this repository for more examples of usage: simple fields resolvers, DI Container support, TypeORM integration, automatic validation, etc.
The Tests folder might also give you some tips how to get various things done.
Currently released version is a MVP (Minimum Viable Product). It is well tested (95% coverage, 4400 lines of test code) and has 90% of the planned features already implemented. However there's some work to do before 1.0.0 release and it's mostly about documentation (website, api reference and jsdoc).
There are also plans for more features like better TypeORM and dataloader integration or middlewares and custom decorators support - the full list of ideas is available on the GitHub repo. You can also keep track of development's progress on project board.
I encourage you to give it a try and experiment with TypeGraphQL. If you have any question, you can ask about it on gitter. If you find a bug, please report it as an issue on GitHub. If you have an interesting feature request, I will be happy to hear about it.
PRs are welcome, but first check, test and build your code before committing it.
- Use commit rules: For more information checkout this commit rule guide.
- Allowing changes to a pull request branch created from a fork
If you want to add a new big feature, please create a proposal first, where we can discuss the idea and implementation details. This will prevent wasting of your time if the PR be rejected.