Sending messages with delegates

Delegates.swift

// 1. Declare which messages can be sent to the delegate
// File ProductScreenDelegate.swift

protocol ProductScreenDelegate { 
    //Add arguments if you need to send some information
    func onProductScreenDismissed()
    func onProductSelected(_ product: Product?)
}


// 2. Call the delegate when you need to send him a message
// File ProductPresenter.swift

class ProductPresenter {
    
    // MARK: Properties
    
    weak var view: ProductView?
    var router: ProductWireframe?
    var interactor: ProductUseCase?
    var delegate: ProductScreenDelegate?
}
    
extension ProductPresenter: ProductPresentation {
    //View told Presenter that view disappeared
    func onViewDidDisappear() {
        //Presenter told its delegate that the screen was dismissed
        delegate?.onProductScreenDismissed()
    }   
}

// 3. Implement the delegate protocol to do something when you receive the message
// File ScannerPresenter.swift

class ScannerPresenter  {
...
}

extension ScannerPresenter: ProductScreenDelegate {
    //Presenter receives the message from the sender
    func onProductScreenDismissed() {
        //Presenter tell view what to do once product screen was dismissed
        view?.startScanning()
    }
    ...
}

// 4. Link the delegate from the Product presenter in order to proper initialize it
// File ScannerRouter.swift
class ProductRouter {

    static func setupModule(delegate: ProductScreenDelegate?) -> ProductViewController {
        ...
        let presenter = ScannerPresenter()
        
        presenter.view = view
        presenter.interactor = interactor
        presenter.router = router
        presenter.delegate = delegate     // Add this line to link the delegate
        ...
        
    }
}