I removed the reposViewModel variable from:

• func reposViewModel(_ reposViewModel: ReposViewModel, isLoading: Bool)
• func reposViewModel(_ reposViewModel: ReposViewModel, didReceiveRepos repos:)
• func reposViewModel(_ reposViewModel: ReposViewModel, didSelectId id: Int)

Delegate methods

Could you explain more about this implementation.

func transform(input: SearchViewModel.Input) -> SearchViewModel.Output {

I could not understand well. The ViewModel is some sort of pipeline that for an input it generates one output?

Hi, I have problem when I want to build the RXswift project in this Repository. I had cloned this repository and installed / updated the pods. When I build the project, those are some error occurred. The error is: Static member 'load' cannot be used on instance of type 'AtomicInt' What should I do to fix the error?

Hi, @tailec

ViewModel has a reference of abstracted ViewController as Delegate in mvvm-delegation. It means that is not MVVM, actually that is MVP. @amadeu01 mentioned in https://github.com/tailec/ios-architecture/pull/2#issuecomment-459971301 , too.

I have a doubt about https://github.com/tailec/ios-architecture/pull/2#issuecomment-460280849 .

I think in MVP, presenter can have access to view (imports UIKit) but view models in MVVM are forbidden to do that.

I think differences between MVP and MVVM are those have references of View directly or not.

Presenter in MVP

Presenter has a reference of View (or ViewController) that is abstracted as protocol in almost cases. To reflect state of Presenter, it calls method of abstructed View.

protocol CounterView {
    func didChangeCount(_ presenter: CounterPresenter, count: Int)
}

class CounterViewController: UIViewController, CounterView {
    let presenter: CounterPresenter
    let countLabel: UILabel

    override func viewDidLoad() {
        super.viewDidLoad()

        presenter.view = self
    }

    func countUp() {
        presenter.countUp()
    }
}

extension CounterViewController: CounterView {
    func didChangeCount(_ presenter: CounterPresenter, count: Int) {
        countLabel?.text = "\(count)"
    }
}

class CounterPresenter {
    private(set) var count: Int = 0 {
        didSet {
             view?.didChangeCount(self, count: count)
        }
    }

    weak var view: CounterView?

    func countUp() {
        count += 1
    }
}

ViewModel in MVVM

ViewModel must not depend on View (or ViewController). Even if View is abstracted as Protocol, ViewModel must not depend on them. To reflect state of ViewModel, it notifies changes of state with closure (or RxSwift.Observable and so on). Closure is implemented outside of ViewModel, therefore ViewModel does not depend on View directly.

class CounterViewController: UIViewController {
    let viewModel: CounterViewModel
    let countLabel: UILabel

    override func viewDidLoad() {
        super.viewDidLoad()

        viewModel.countChanged = { [weak countLabel] count in
            countLabel?.text = "\(count)"
        }
    }

    func countUp() {
        viewModel.countUp()
    }
}

class CounterViewModel {
    private(set) var count: Int = 0 {
        didSet {
             countChanged?(count)
        }
    }

    var countChanged: ((Int) -> Void)?

    func countUp() {
        count += 1
    }
}