GenericPass.swift

import UIKit

protocol MessageDelegate: AnyObject {
    func didPressButton() -> Void
}

/// Represents a view that will send messages, e.g. button presses.
final class SenderView<MyMessageDelegate: MessageDelegate>: UIView {
    
    private let myButton: UIButton
    
    public weak var messageDelegate: MyMessageDelegate? = nil
    
    @MainActor
    init() {
        self.myButton = .init()
        super.init(frame: .zero)
        let action = UIAction { [weak self] (action) in
            /// TODO: Send message to `ReceiverView`...
            self?.messageDelegate?.didPressButton()
        }
        myButton.addAction(action, for: .touchUpInside)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

/// Represents a view that responds to events.
final class ReceiverView: UIView {
    
    @MainActor
    init() {
        super.init(frame: .zero)
    }
    
    func didReceiveMessage() {
        print("Got a message from SenderView!")
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

extension ReceiverView: MessageDelegate {
    func didPressButton() {
        self.didReceiveMessage()
    }
}

/// Represents some controller coordinating senders and receivers.
final class MyViewController : UIViewController {
    
    let senderView: SenderView<ReceiverView>
    let receiverView: ReceiverView
    
    @MainActor
    init() {
        senderView = .init()
        receiverView = .init()
        super.init(nibName: nil, bundle: nil)
        
        view.addSubview(senderView)
        view.addSubview(receiverView)
        
        /// Layout stuff here...
        
        /// TODO: connect sender to receiver...
        senderView.messageDelegate = receiverView
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}