Injecting value to resolver

Quite often we need to have access to graphql context inside resolver. Common example could be field like viewer

{
  viewer {
    me {
      username
    }
  }
}

Built-in injectors @Context, @Source, @Info

There are 3 argument decorators in typegql that allow passing values to resolvers - @Context, @Source, @Info

Implementation of Viewer type would use @Context decorator to get user id from graphql context and could look like:

import { ObjectType, Field, Context } from 'typegql';

@ObjectType()
class Viewer {
  @Field({ type: () => Person })
  me(@Context context) {
    return db.findUserById(context.currentUser.id);
  }
  @Field() id: number;
}

Custom injector with @Inject

Beside built-in injectors you can use @Inject decorator to pass any value to given argument.

@Inject decorator requires getter function that converts resolve info to any arbitral value. Note you can return promise of any value, too.

import { ObjectType, Field, Inject } from 'typegql';

@ObjectType()
class Viewer {
  @Field({ type: () => Person })
  me(@Inject({source, args, context, info} => 42) someNumber: number): number {
    return someNumber; // it will be 42;
  }
  @Field() id: number;
}

Notes

• Decorated arguments are not present in args list of field schema definition.