Leveraging Swift Package Manager to Maintain Clean Architecture Layers in iOS Development — Part 2

DomainLayer Implementation

Leveraging Swift Package Manager to Maintain Clean Architecture Layers in iOS Development — Part 1

Lets build our DomainLayer from Dependency Diagram above.

First lets define DomainLayer Contract with Protocol, we need 2 protocol that is CharacterRepository and CharacterListUsecase.

public protocol CharacterRepository {
    func getCharacters() async throws -> ListModel<CharacterModel>
}

public protocol CharacterListUsecase {
    func execute() async throws -> ListModel<CharacterModel>
}

DomainLayer  
│  
├── Repositories  
│   ├── CharacterRepository
│  
├── Usecases
│   ├── CharacterListUsecase

Then we need to define Models that will consume by PresentationLayer and built by DataLayer. (We use Rick and Morty API)

public struct ListModel<T: Sendable>: Sendable {
    public let results: [T]
    
    public init(results: [T]) {
        self.results = results
    }
}

public struct CharacterModel: Sendable {
    public let id: Int
    public let name: String
    public let status: String
    public let species: String
    public let gender: String
    public let image: String
    
    public init(id: Int, name: String, status: String, species: String, gender: String, image: String) {
        self.id = id
        self.name = name
        self.status = status
        self.species = species
        self.gender = gender
        self.image = image
    }
}

Because we will consume it to ViewModel that implement MainActor we cant just use Array CharacterModel, we need to wrap it to sendable object that is why we create ListModel here.

DomainLayer  
│  
├── Models
│   ├── ListModel
│   ├── CharacterModel
│  
├── Repositories  
│   ├── CharacterRepository
│  
├── Usecases
│   ├── CharacterListUsecase

After that we can implement Usecases or concrete type of CharacterListUsecase.

public final class CharacterListUsecaseImpl: CharacterListUsecase {
    private let characterRepository: CharacterRepository
    
    public init(characterRepository: CharacterRepository) {
        self.characterRepository = characterRepository
    }
    
    public func execute() async throws -> ListModel<CharacterModel> {
        try await characterRepository.getCharacters()
    }
}

We can add Mock also, for #Preview and Test later.

public final class CharacterListUsecaseMock: CharacterListUsecase {
    public init() {}
    
    public func execute() async throws -> ListModel<CharacterModel> {
        return ListModel(results: [
            CharacterModel(id: 1, name: "Rick Sanchez", status: "Alive", species: "Human", gender: "Male", image: "https://rickandmortyapi.com/api/character/avatar/1.jpeg"),
            CharacterModel(id: 2, name: "Morty Smith", status: "Alive", species: "Human", gender: "Male", image: "https://rickandmortyapi.com/api/character/avatar/2.jpeg")
        ])
    }
}

Final structure will be like this

DomainLayer  
│  
├── Models
│   ├── ListModel
│   ├── CharacterModel
│  
├── Repositories  
│   ├── CharacterRepository
│  
├── Usecases
│   ├── CharacterListUsecase
│   ├── CharacterListUsecaseImpl
│   ├── CharacterListUsecaseMock

Dependency Diagram