NestJs Swagger: How to define Api Property for dynamic classes

Question

I have below class

export class DocumentsSteps {
    @ApiProperty({type: ???})
    [type: string]: DocumentStep;
}

How should I define ApiProperty type?

Capsule

Answer 1

As of right now (9/21/2021), this isn't possible with Nest's @nestjs/swagger library, due to the fact that there's no field to reflect metadata on. There may be an opportunity to open a pull request to allow for the use of dictionaries with the library, but right now your best bet would be modifying the swagger document that Nest generates and adding it on your own at the moment

Agathaagathe

would you please add a small sample here about the changes manually, what should it look like – Capsule

Answer 2

You can wrap it with a function

export type Constructor<I> = new (...args: any[]) => I

function ErrorDto(statusCode: number, message: string): Constructor<Error>{
  class Error implements Error{
    @ApiProperty({ example: statusCode })
    readonly statusCode: number

    @ApiProperty({ example: message })
    readonly message: string

  }
  return Error
}
export class UnauthorizedErrorDto extends ErrorDto(401, 'Unauthorized'){}
export class BadRequestErrorDto extends ErrorDto(400, 'Bad Request'){}

Truism

Answer 3

I found a solution for this, it looks a little ugly on swagger but it's the best possible way.

Using additionalProperties, you can add dynamic keys, with a typed value by providing a reference to your Dto. The Dto will not be a part of some other response and may not be available in swagger, to expose it, we need to use @ApiExtaModels()

@ApiExtraModels(DocumentStep)
export class DocumentsSteps {
    @ApiProperty({
        additionalProperties: { oneOf: [{ $ref: getSchemaPath(DocumentStep) }] },
    })
    [type: string]: DocumentStep;
}

The result looks like this

Isolda

Answer 4

Check this out

https://docs.nestjs.com/custom-decorators#decorator-composition

You could implement another decorator to extends the ApiProperty

export function CustomApiProperty(type: string) {
  return applyDecorators(
    ApiProperty({type, ...}),
  );
}

Lend