Resolver Example.swift

import Foundation
import SwiftUI
import Combine
import Resolver

// MARK: - Presentation Layer

struct MyView: View {
    @ObservedObject var viewModel: MyViewModel

    var body: some View {
        Text(viewModel.data)
    }
}

// MARK: - Domain Layer

class MyViewModel: ObservableObject {
    @Published var data: String = ""
    @Injected private var dataFetcher: DataFetcher
    private var cancellable: AnyCancellable?


    func fetchData() {
        // Fetch data from the network or a local database
        // using the data access layer
        func fetchData() {
               cancellable = dataFetcher.fetchData()
                   // Handle the result of the fetch
                   .receive(on: RunLoop.main)
                   .sink { error in
                       if case let .failure(error) = error {
                           print(error.localizedDescription)
                       }
                   } receiveValue: { (value: String) in
                       self.data = value
                   }
           }
    }
}


// MARK: - Data Access Layer
protocol DataFetcher {
    func fetchData() -> AnyPublisher<String, Error>
}

class NetworkDataFetcher: DataFetcher {
    func fetchData() -> AnyPublisher<String, Error> {
        // Fetch data from the network and call the completion handler
        Just("Hello")
            .setFailureType(to: Error.self)
            .eraseToAnyPublisher()
    }
}

class DatabaseDataFetcher: DataFetcher {
    func fetchData() -> AnyPublisher<String, Error> {
        // Fetch data from the local database and call the completion handler
        Just("Mom")
            .setFailureType(to: Error.self)
            .eraseToAnyPublisher()
    }
}

// MARK: - Dependency Injection

extension Resolver {
    public static func registerMyViewModel() {
        register { MyViewModel(dataFetcher: $0) }
            .implements(MyViewModel.self)
            .resolve(using: DataFetcher.self)
    }
}