Having a custom getter in a Response DTO does not function properly

Question

Having a custom getter in a Response DTO does not function properly

After attempting to create a custom getter as shown below:

import { Expose } from 'class-transformer';

export class MyDTOResponse {
  @Expose()
  id: string;

  @Expose()
  name: string;

  @Expose()
  get thisIsATest(): string {
    return 'yolo';
  }
}

This is the process I follow for transformation:

plainToClass(MyDTOResponse, MyRawDataObject, {
  excludeExtraneousValues: true,
});

Referencing the documentation at https://github.com/typestack/class-transformer#exposing-getters-and-method-return-values, my resulting response only contains:

{
  "id": "f8c213c7-5853-4d01-b424-cb0349a6c580",
  "name": "Clean the kitchen!"
}

I am unsure of the mistake I made, but the "thisIsATest" property seems to be missing.

javascript typescript class-transformer

Answer 1

Answer №1

plainToClass function will generate a new instance. If you log this instance, the "thisIsATest" property won't be visible. You can test it with the provided code snippet:

const result = plainToClass(MyDTOResponse, MyRawDataObject, {
  excludeExtraneousValues: true,
});

console.log(result.thisIsATest); // yolo

console.log(instanceToPlain(result))
// {
//   id: 'f8c213c7-5853-4d01-b424-cb0349a6c580',
//   name: 'Clean the kitchen!',
//   thisIsATest: 'yolo'
// }

By the way, it is recommended to use the plainToInstance method as plainToClass is now deprecated.

Answer 2

plainToClass function will generate a new instance. If you log this instance, the "thisIsATest" property won't be visible. You can test it with the provided code snippet:

const result = plainToClass(MyDTOResponse, MyRawDataObject, {
  excludeExtraneousValues: true,
});

console.log(result.thisIsATest); // yolo

console.log(instanceToPlain(result))
// {
//   id: 'f8c213c7-5853-4d01-b424-cb0349a6c580',
//   name: 'Clean the kitchen!',
//   thisIsATest: 'yolo'
// }

By the way, it is recommended to use the plainToInstance method as plainToClass is now deprecated.

Answer 3

Answer №2

Utilizing the Transform decorator allows you to achieve this objective by eliminating the need for the getter method,

an example implementation can be seen below:


import { Expose } from 'class-transformer';

export class MyDTOResponse {
  @Expose()
  id: string;

  @Expose()
  name: string;

  @Expose()
  @Transform(({ value, key, obj, type }) => 'yolo' )
  thisIsATest: string

  @Expose()
  @Transform(({ value, key, obj, type }) => obj.name )
  thisIsATestB: string
}

For further details, refer to the following link:

Explore advanced usage of transform feature

Answer 4

Utilizing the Transform decorator allows you to achieve this objective by eliminating the need for the getter method,

an example implementation can be seen below:


import { Expose } from 'class-transformer';

export class MyDTOResponse {
  @Expose()
  id: string;

  @Expose()
  name: string;

  @Expose()
  @Transform(({ value, key, obj, type }) => 'yolo' )
  thisIsATest: string

  @Expose()
  @Transform(({ value, key, obj, type }) => obj.name )
  thisIsATestB: string
}

For further details, refer to the following link:

Explore advanced usage of transform feature

Having a custom getter in a Response DTO does not function properly

Answer №1

Answer №2

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