CombinePass.swift

import UIKit
import Combine

final class MessageConduit {
    public let messageSubject = PassthroughSubject<Void, Never>()
}

/// Represents a view that will send messages, e.g. button presses.
final class SenderView: UIView {
    
    private let myButton: UIButton
    
    private let conduit: MessageConduit
    
    @MainActor
    init(conduit: MessageConduit) {
        self.myButton = .init()
        self.conduit = conduit
        super.init(frame: .zero)
        let action = UIAction { [weak self] (action) in
            /// TODO: Send message to `ReceiverView`...
            self?.conduit.messageSubject.send(Void())
        }
        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 {
    
    private let conduit: MessageConduit
    
    @MainActor
    init(conduit: MessageConduit) {
        self.conduit = conduit
        super.init(frame: .zero)
    }
    
    func didReceiveMessage() {
        print("Got a message from SenderView!")
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

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