Nestjs: Cast complex Entity to Dto - mapping

Question

I'm trying to cast a complex Entity to a Dto. I would like to remove some values which are in the entity from the DTO.
My entity looks like this (For simplicity a large part of the entity is omitted):
export class ResultEntity {
constructor(
public id: string,
public userId: string,
public results: CalculationOutputEntity[] = [],
public item: Item = new Item(),
) { }
}
export class Item {
constructor(
public privat: Private = new Private(),
public state: State = new State(),
public combined: number = 0,
) { }
}
export class State {
constructor(
public numberA: number = 0,
public numberB: number = 0,
public numberC: number = 0,
public numberD: number = 0,
) { }
}
I have found a solution which works very well for simple entities: Cast entity to dto
If I adopt this suggestion of the custom interceptor, removing the id or the whole item property works.
I have tried two possibilities tot define my DTOs:
It returns only the id and the item as a whole.
#Exclude()
export class AdvisoryResultDto {
#Expose()
public id: string;
public userId: string;
public results: CalculationOutputDto[];
#Expose()
public item: Item;
}
This solution returns everything except the item property.
export class AdvisoryResultDto {
public id: string;
public userId: string;
public results: CalculationOutputDto[];
#Exclude()
public item: Item;
}
The problem now is that I want to remove only certain values within the item property. So for example the private field and within the state-property numberB.
I would like to have the possibility within the nested classes to remove single values also with Exclude().
So for example:
export class AdvisoryResultDto {
public id: string;
public userId: string;
public results: CalculationOutputDto[];
public item: Item;
}
export class Item {
#Exclude()
public privat: PrivateDto;
public state: StateDto;
public combined: number;
}
export class StateDto {
public numberA: number;
#Exclude()
public numberB: number;
public numberC: number;
public numberD: number;
}
Unfortunately I can't find anything about this exact problem. To take over the mapping manually would also not be a solution, since the CalculationOutput is by far more complex and is nested with many classes and properties.
Am I just missing a small step or is it not possible with Expose and Exclude from the class-transformer? If not I would appreciate another solution.

Answer 1

So i found the soulution in the documentation of the class-transformer package: https://github.com/typestack/class-transformer#working-with-nested-objects
I need to add the #Type-Decorator to nested classes
The solution:
#Expose()
export class AdvisoryResultDto {
public id: string;
public userId: string;
public results: CalculationOutputDto[];
#Type(() => Item)
public item: Item;
}
export class Item {
#Exclude()
#Type(() => PrivateDto)
public privat: PrivateDto;
#Expose()
#Type(() => StateDto)
public state: StateDto;
public combined: number;
}
export class StateDto {
public numberA: number;
#Exclude()
public numberB: number;
public numberC: number;
public numberD: number;
}

Answer 2

Why not make a constructor and then initalize DTO with only the required values from the entity? Just pass the entity object to DTO's constructor and remove the fields from DTO.