DTO Schema

buildFieldSchemaFromDto(dtoClass) reads Swagger metadata from DTO classes and returns a FieldSchema.

class UserDTO {
  @ApiProperty()
  id!: string;

  @ApiProperty({ type: () => ProfileDTO })
  profile!: ProfileDTO;
}

const schema = buildFieldSchemaFromDto(UserDTO);

Swagger-decorated nested DTO classes become relation fields. Recursive DTO references are cut off with an empty nested schema to avoid infinite traversal.

Metadata Requirements

• Only properties decorated with @ApiProperty or compatible Swagger metadata are included.
• DTO classes without Swagger property metadata produce an empty schema.
• Nested DTO classes become relation schema nodes when their type metadata points to another Swagger-decorated DTO.
• Arrays of DTOs are supported when Swagger exposes the array item type, for example with @ApiProperty({ type: () => [BookDTO] }).
• Recursive references are cut off with an empty nested relation schema.

Use a manual schema with relation when the public response shape differs from Swagger metadata.

getDtoFields

const fields = getDtoFields(UserDTO);

getDtoFields returns the Swagger-decorated property names for a DTO class. DTOs without Swagger property metadata return an empty array.