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CreateGraphQL schema and resolvers withTypeScript, using classes and decorators!

https://typegraphql.com

TypeGraphQL makes developing GraphQL APIs an 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 a kind of DTO class.For example, to declareRecipe type we simply create a class and annotate it with decorators:

@ObjectType()classRecipe{  @Field(type=>ID)id:string;  @Field()title:string;  @Field(type=>[Rate])ratings:Rate[];  @Field({nullable:true})averageRating?:number;}

And we get the corresponding part of the schema in SDL:

typeRecipe {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 and auth guards:

@Resolver(Recipe)classRecipeResolver{// dependency injectionconstructor(privaterecipeService:RecipeService){}  @Query(returns=>[Recipe])recipes(){returnthis.recipeService.findAll();}  @Mutation()  @Authorized(Roles.Admin)// auth guardremoveRecipe(@Arg("id")id:string):boolean{returnthis.recipeService.removeById(id);}  @FieldResolver()averageRating(@Root()recipe:Recipe){returnrecipe.ratings.reduce((a,b)=>a+b,0)/recipe.ratings.length;}}

And in this simple way, we get this part of the schema in SDL:

typeQuery {recipes: [Recipe!]!}typeMutation {removeRecipe(id:String!):Boolean!}

We all know that GraphQL is great and solves many problems we have with REST APIs, like Over-Fetching and Under-Fetching. But developing a GraphQL API in Node.js with TypeScript is sometimes a bit of a pain. Why? Let's take a look at the steps we usually have to take.

First, we create all the GraphQL types inschema.graphql using SDL. Then we create our data models usingORM classes, which represent 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 implement the resolvers using weird generic signatures and manually performing common tasks, like validation, authorization and loading dependencies:

exportconstgetRecipesResolver:GraphQLFieldResolver<void,Context,GetRecipesArgs>=async(_,args,ctx,)=>{// common tasks repeatable for almost every resolverconstrepository=TypeORM.getRepository(Recipe);constauth=Container.get(AuthService);awaitjoi.validate(getRecipesSchema,args);if(!auth.check(ctx.user)){thrownewNotAuthorizedError();}// our business logic, e.g.:returnrepository.find({skip:args.offset,take:args.limit});};

The biggest problem is 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 for 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 the field name? The rename feature (F2) won't work correctly.

Tools likeGraphQL Code Generator orgraphqlgen only solve the first part - they generate the corresponding interfaces (and resolvers skeletons) for our GraphQL schema but they don't fix the schema <--> models redundancy and developer experience (F2 rename won't work, you have to remember about the codegen watch task in the background, etc.), as well as common tasks like validation, authorization, etc.

TypeGraphQL comes to address these issues, based on experience from a few years of developing GraphQL APIs in TypeScript. The main idea is to have only one source of truth by defining the schema using classes and some help from decorators. Additional features like dependency injection, validation and auth guards help with common tasks that normally we would have to handle ourselves.

The documentation, installation guide, and detailed description of the API and all of its features areavailable on the website.

A full getting started guide with a simple walkthrough (tutorial) can be found atgetting started docs.

If you prefer video tutorials, you can watchBen Awad'sTypeGraphQL video series on YouTube.

You can also check theexamples folder in this repository for more examples of usage: simple fields resolvers, DI Container support, TypeORM integration, automatic validation, etc.

TheTests folder might also give you some tips on how to get various things done.

To report a security vulnerability, please use theTidelift security contact.Tidelift will coordinate the fix and disclosure.

The currently released version is a stable 1.0.0 release. It is well-tested (97% coverage, ~500 test cases) and has most of the planned features already implemented. Plenty of companies and independent developers are using it in production with success.

However, there are also plans for a lot more features like better TypeORM, Prisma and DataLoader integration, custom decorators and metadata annotations support -the full list of ideas is available on the GitHub repo. You can also keep track ofdevelopment's progress on the project board.

If you have any interesting feature requests, feel free to open an issue on GitHub so we can discuss that!

TypeGraphQL is an MIT-licensed open-source project. This framework is a result of the tremendous amount of work - sleepless nights, busy evenings and weekends.

It doesn't have a large company that sits behind it - its ongoing development is possible only thanks to the support of the community.

Please ask your company to support this open source project bybecoming a gold sponsor and getting a premium technical support from our core contributors.

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