First layer - translations layer

👤 DTO 📝 Types

What for?

DTO (Data Transfer Object) layer is used for e.g.:

currently logged in user

FetchUserResponse -> new UserDto(response) -> UserFactory.fromUserDto(dto)

* factory from domain layer

list of users

FetchUserListResponse -> new UserListDto(response) -> dto.users.map(user => new UserListItem(user))

* UserListItem from domain layer

👾

REMBER don't use same model for 2 things. User isn't UserListItem.

DTO

DTO - Data Transfer Object - it is a class that is resposible for tranlsating incoming responses to our models.

Example DTOs: find-users.dto.ts, user-profile.dto.ts, user.dto.ts.

ℹ️

DTO/Translations layer is responsible for managing incoming data shape and encapsulating changes.

class UserDto {
    id: UserID
    username: string
    address: AddressDto
 
    constructor(response: FetchUserResponse) {
      this.id = response.id
      this.username = response.user_name
      this.address = AddressDto.fromFetchUserResponse(response)
    }
 
    static fromResponse(res: FetchUserResponse): UserDto {
      return new UserDto(res)
    }
}

Types

Types in translation layer are:

responses
inner types, like UserID

type UserID = string
 
type FetchUserResponse = {
  id: UserID
  username: string
  address: AddressResponseObject
}
 
type AddressResponseObject = {
  street: string;
  city: string;
}

Example

Example common feature: users

- user-id.ts
- fetch-user-response.ts
user.dto.ts
address.dto.ts

class UserDto {
  id: UserID;
  username: string;
  address: AddressDto;
 
  constructor(response: FetchUserResponse) {
    this.id = response.id;
    this.username = response.user_name;
    this.address = AddressDto.fromFetchUserResponse(response);
  }
 
  static fromResponse(res: FetchUserResponse): UserDto {
    return new UserDto(res);
  }
}