class-validator validate nested object based on parent properties NestJs

Question

I want to get value of type property in class B for validate class A.

Class A is used as a property type for the property a in Class B.

class Content1 {}

class Content2 {}

class A {
  @IsValidContent()
  content: Content1 | Content2;
}

class B {
  @Type(() => A)
  @ValidateNested({ each: true })
  a: A;

  type: string;
}

export function IsValidContent(validationOptions?: ValidationOptions) {
  return (object: Object, propertyName: string) => {
    registerDecorator({
      name: "isValidContent",
      target: object.constructor,
      propertyName,
      constraints: [],
      options: validationOptions,
      validator: {
        validate(value: any, args: ValidationArguments) {

          const type = args.object["type"]; // how to get type properties from parent
          switch (type) {
            case "X":
              return isValidType(value, Content1);
            case "Y":
              return isValidType(value, Content2);
            default:
              return false;
          }
        },
      },
    });
  }
}

How to get type properties from class B in order to validate the property content in class A?

Validation decorator is IsValidContent

@CharchitKapoor Yes, the args variable only contains properties of the child class. I cant get type property of the parent class — Lang Minh Nguyên
– Lang Minh Nguyên, Commented May 7, 2023 at 10:23
My current solution is to validate in the parent class, and then retrieve the value of the parent class to call the value of the child class — Lang Minh Nguyên
– Lang Minh Nguyên, Commented May 7, 2023 at 10:26

M0ngi · Accepted Answer · 2023-07-16 20:14:38Z

i have the same problem.

I have created a validator that add parent object in each child:

import { Exclude } from 'class-transformer';
import {
  Validate,
  ValidationArguments,
  ValidationOptions,
  ValidatorConstraint,
  ValidatorConstraintInterface,
} from 'class-validator';

@ValidatorConstraint({ name: 'customValidator', async: false })
export class AddParentRefConstraint implements ValidatorConstraintInterface {
  defaultMessage(): string {
    return '';
  }

  validate(
    obj: object,
    validationArguments: ValidationArguments,
  ): Promise<boolean> | boolean {
    // add the parent ref on obj
    const parentRef = new WeakRef(validationArguments.object);
    Object.defineProperty(obj, 'parentRef', {
      get: function () {
        return parentRef;
      },
    });
    Exclude()(obj, 'parentRef');
    return true;
  }
}

export function AddParentRef(validationOptions?: ValidationOptions) {
  return function (target: object, propertyKey: string | symbol) {
    return Validate(AddParentRefConstraint, validationOptions)(
      target,
      propertyKey,
    );
  };
}

A parentRef member is added in each object where the annotation is needed. Next, you can use it. I have using the @Exclude of class-transfomer on the property to ensure that the field if removed from serialisation, but if you you custom serialization, you should take care of it.

Next you can do this:

class Content1 {}

class Content2 {}

class A {
  @IsValidContent()
  content: Content1 | Content2;
}

class B {
  @AddParentRef()
  @Type(() => A)
  @ValidateNested({ each: true })
  a: A;

  type: string;
}

export function IsValidContent(validationOptions?: ValidationOptions) {
  return (object: Object, propertyName: string) => {
    registerDecorator({
      name: "isValidContent",
      target: object.constructor,
      propertyName,
      constraints: [],
      options: validationOptions,
      validator: {
        validate(value: any, args: ValidationArguments) {

          const type = args.object.parentRef["type"];
          switch (type) {
            case "X":
              return isValidType(value, Content1);
            case "Y":
              return isValidType(value, Content2);
            default:
              return false;
          }
        },
      },
    });
  }
}

Nice answer, i think u can improve this feature on class-validator github

M0ngi · Accepted Answer · 2023-07-18 18:33:45Z

-1

You can use the getParentObject method provided by ValidationArguments to get the parent object of the current property being validated. You can then access the type property of class B to use it in the IsValidContent decorator. here is the updated IsValidContent decorator:

export function IsValidContent(validationOptions?: ValidationOptions) {
  return (object: Object, propertyName: string) => {
    registerDecorator({
      name: "isValidContent",
      target: object.constructor,
      propertyName,
      constraints: [],
      options: validationOptions,
      validator: {
        validate(value: any, args: ValidationArguments) {
          const parentObject = args.getParentObject();
          const type = parentObject["type"];
          switch (type) {
            case "X":
              return isValidType(value, Content1);
            case "Y":
              return isValidType(value, Content2);
            default:
              return false;
          }
        },
      },
    });
  };
}

I hope this help you.

edited Jul 18, 2023 at 18:33

M0ngi

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answered May 8, 2023 at 16:33

Omid Deldar

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3 Comments

Lang Minh Nguyên Over a year ago

Property 'getParentObject' does not exist on type 'ValidationArguments'

Omid Deldar Over a year ago

try this: const parentObject = args.object as B; const type = parentObject.type;

Lang Minh Nguyên Over a year ago

args.object not included any class B properties

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