Custom decorators

Custom decorators allow you to improve your developer experience and reduce code boilerplate.

Here is an extremely simple FieldID decorator:

app/graphql/decorators.ts

export function FieldID(options: FieldOptions = {}) {
  return Field(() => ID, {
    description: 'Resource identifier in the UUID V4 format',
    ...options,
  })
}

@ObjectType()
export class User {
  @FieldID()
  id: string

  @FieldID()
  organizationId: string
}

Method decorators

We've seen that middlewares allow us to reuse some code between resolvers. To further reduce the boilerplate and improve the API we can create our own custom method decorators.

app/graphql/decorators.ts

export function LogExecutionTiming() {
  return createMethodMiddlewareDecorator(async (_, next) => {
    const start = Date.now()
    const result = await next()
    const diff = Date.now() - start
    this.logger.info(`took ${diff}ms`)
    return result
  })
}

@Resolver()
class RecipeResolver {
  @LogExecutionTiming()
  @Query()
  createRecipe() {}
}

Class decorators

Similar to method decorators, we can create our own custom resolver class decorators

app/graphql/decorators.ts

export function ValidateRequestIp(ips: string[]) {
  return createResolverClassMiddlewareDecorator(async ({ context }, next) => {
    if (!ips.includes(context.request.ip())) {
      throw new UnauthorizedIpException()
    }

    return next()
  })
}

@ValidateRequestIp('127.0.0.1')
@Resolver()
class InternalResolver {
  @Query()
  localhostOnly() {}
}

Method decorators

Class decorators

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