如何使用 GraphQL 在 NestJS 中创建自定义字段验证装饰器

Question

I'm working on a NestJS API with apollo-server-express and I have the next InputType for appointments:

@InputType()
export class AppointmentInput {
    @Field(of => String)
    @IsNotEmpty()
    name: string;

    @Field(of => String)
    @IsNotEmpty()
    @IsDateString()
    dateStart: string;

    @Field(of => String)
    @IsNotEmpty()
    @IsDateString()
    dateEnd: string;

    @Field(of => Boolean)
    @IsBoolean()
    paid: boolean;

    @Field(of => Int)
    idDoctor: number;
    
    @Field(of => Int)
    idPatient: number;
    @Field(of => Int)
    idService: number;
}

Let's say I want to validate if the name has some "a" letter with a Pipe:

import { PipeTransform, Injectable, ArgumentMetadata, HttpException, HttpStatus } from '@nestjs/common';

@Injectable()
export class NamePipe implements PipeTransform<string, string>{
  transform(name: string, metadata: ArgumentMetadata) {
    if (name.includes('a')) {
      throw new HttpException('The name has an a', HttpStatus.BAD_REQUEST);
    }
    return name;
  }
}

But if use it like this:

@Field(of => String)
@IsNotEmpty()
@UsePipes(NamePipe)
name: string;

It throws me the next error:

The return type of a property decorator function must be either 'void' or 'any'. Unable to resolve signature of property decorator when called as an expression. Type 'TypedPropertyDescriptor' is not assignable to type 'void'.

How can I solve this and use custom decorators to validate my fields? Also is important that my decorators can call services, because maybe in the future I want to validate for example the role id, and check if in the database exists a role with that id and if not throw an error.

Answer 1

I think you should rather create a custom class-validator decorator and use it like any class-validator decorator, assuming you've already applied a global NestJS validation pipe