question: can we perform a oneOf validation?

Description

How to perform a oneOf validation of a nested object i.e., child object is either of TypeA or TypeB? This seems like a very common use case, is there an out-of-the-box solution for this? I understand that this problem is concerning class-transformer more than it is class-validator…

Is there an example of a generic @OneOf()decorator? Any ideas on how to work with class-transformer and class-validator together to make this happen?

Reproduction

class TypeA {

    @IsString()
    public foo;
}

class TypeB {

    @IsString()
    public bar;
}

class Parent {

    @IsObject()
    @ValidateNested()
    @Type((): Function => TypeA)  // ???
    public child: TypeA | TypeB;
}

Environment

• nodejs: 8.11.2
• browser
• framework/library

class-validator version: 0.12.2

[ibraah88]

@mehtamanan can you try this ?

import {
  registerDecorator,
  ValidationOptions,
  ValidatorConstraint,
  ValidatorConstraintInterface,
  ValidationArguments,
} from 'class-validator';
import { activitiesList } from '../activitiesList';

@ValidatorConstraint({ async: true })
export class OneOfConstraint implements ValidatorConstraintInterface {
  validate(activities: any, args: ValidationArguments) {
   return Array.isArray(activities)
      ? activities.every(item => activitiesList.includes(item))
      : false;
  }
}

export function OneOf(validationOptions?: ValidationOptions) {
  return function(object: Object, propertyName: string) {
    registerDecorator({
      target: object.constructor,
      propertyName: propertyName,
      options: validationOptions,
      constraints: [],
      validator: OneOfConstraint,
    });
  };
}

---

and to use it in your DTO

...
import { activities } from '../activities';
...

  @IsArray()
  @IsNotEmpty()
  @OneOf({
    message: `activities must be in: ${activities}`,
  })
  activities: string[];

[github-actions[bot]]

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