Utilizing generics with Swagger in NestJS

Question

Utilizing generics with Swagger in NestJS

export class PaginatedResult<T> {

 @Expose()
 @ApiResponseProperty(type: T}) // It's unfortunate that this isn't working because it's a type but being used as a value
 @Transform(({ obj }) =>
  obj.data.map((data) => new obj.classConstructor(data)),
 )
 data: T[];
}

The data is of Type T, which includes options such as Item or Tag and more. However, Swagger only displays Item even on endpoints where the ResponseType is defined as:

{type: PaginatedResult<Tag>}

Is there any workaround for this issue?

typescript types swagger nestjs

Answer 1

Answer №1

Instead of referencing the Property directly, I came up with a solution that involves creating a custom ApiResponseDecorator. This decorator takes the generic type as input and populates a schema with it:

This implementation is specifically for NestJs.

export const CustomApiResponse = <GenericType extends Type<unknown>>(data: GenericType ) =>
  applyDecorators(
    ApiExtraModels(ModelWithGeneric, data),
    ApiOkResponse({
      description: `The paginated result of ${data.name}`,
      schema: {
        allOf: [
          { $ref: getSchemaPath(ModelWithGeneric) },
          {
            properties: {
              genericFieldName: {
                type: 'array',
                items: { $ref: getSchemaPath(data) },
              },},},],},}))

You can use it like this:

@Controller('')
export class SomeController {

  @Get('/')
  CustomApiResponse(GenericType)
  async get(): Promise<ModelWithGeneric<GenericType>> {}
}

Answer 2

Instead of referencing the Property directly, I came up with a solution that involves creating a custom ApiResponseDecorator. This decorator takes the generic type as input and populates a schema with it:

This implementation is specifically for NestJs.

export const CustomApiResponse = <GenericType extends Type<unknown>>(data: GenericType ) =>
  applyDecorators(
    ApiExtraModels(ModelWithGeneric, data),
    ApiOkResponse({
      description: `The paginated result of ${data.name}`,
      schema: {
        allOf: [
          { $ref: getSchemaPath(ModelWithGeneric) },
          {
            properties: {
              genericFieldName: {
                type: 'array',
                items: { $ref: getSchemaPath(data) },
              },},},],},}))

You can use it like this:

@Controller('')
export class SomeController {

  @Get('/')
  CustomApiResponse(GenericType)
  async get(): Promise<ModelWithGeneric<GenericType>> {}
}

Utilizing generics with Swagger in NestJS

Answer №1

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