iOS Swift 协议和委托

Question

Why my delegation is not working?

With my sample the action button works when clicked, but for some reason it does not reach the didAction function in my second controller.

protocol HomeControllerDelegate: class {
    func didAction()
}

class HomeController: UIViewController {
    
    weak var delegate: HomeControllerDelegate?
    
    private let actionButton: UIButton = {
        let button = UIButton(type: .system)
        button.setTitle("Action", for: .normal)
        button.setTitleColor(.white, for: .normal)
        button.backgroundColor = .black
        button.setHeight(50)
        button.setWidth(100)
        button.addTarget(self, action: #selector(handleAction), for: .touchUpInside)
        return button
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white
        view.addSubview(actionButton)
        actionButton.centerX(inView: view)
        actionButton.centerY(inView: view)
    }
    
    @objc func handleAction() {
        print("DEBUG: Handle Action Button delegate here....")
        delegate?.didAction()
    }
}

class SecondController: UIViewController {
    
    let homeController = HomeController()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        homeController.delegate = self
    }
}

extension SecondController: HomeControllerDelegate {
    func didAction() {
        print("DEBUG: In SecondController - didAction()")
    }
}

Answer 1

Many thanks for the guidance, it has made me look at the fundamentals and also what to research.

I have created the below which solves my problem.

A container controller that Instantiates two ViewControlers and sets them as childVC's

Then created a protocol on FirstChildVC and SecondChildVC is the delegate

All is working now an I understand a lot better.

class ContainerController: UIViewController {
    
    let secondChildVC = SecondChildVC()
    let firstChildVC = FirstChildVC()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white
        addFirstChildVC()
        addSecondChildVC()
    }
    
    func addSecondChildVC(){
        addChild(secondChildVC)
        view.addSubview(secondChildVC.view)
        secondChildVC.didMove(toParent: self)
        setSecondChildVCConstraints()
    }
    
    func addFirstChildVC(){
        addChild(firstChildVC)
        view.addSubview(firstChildVC.view)
        firstChildVC.delegateActionButton = secondChildVC
        firstChildVC.didMove(toParent: self)
        setFirstChildVCConstraints()
    }
    
    func setFirstChildVCConstraints() {
        firstChildVC.view.translatesAutoresizingMaskIntoConstraints = false
        firstChildVC.view.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 20).isActive = true
        firstChildVC.view.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20).isActive = true
        firstChildVC.view.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20).isActive = true
        firstChildVC.view.heightAnchor.constraint(equalToConstant: 200).isActive = true
    }
    
    func setSecondChildVCConstraints() {
        secondChildVC.view.translatesAutoresizingMaskIntoConstraints = false
        secondChildVC.view.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -20).isActive = true
        secondChildVC.view.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20).isActive = true
        secondChildVC.view.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20).isActive = true
        secondChildVC.view.heightAnchor.constraint(equalToConstant: 200).isActive = true
    }
}

protocol FirstChildVCDelegate: class {
    func didAction(data: String)
}

class FirstChildVC: UIViewController {
    
    weak var delegateActionButton: FirstChildVCDelegate!
    
    private let actionButton: UIButton = {
        let button = UIButton(type: .system)
        let buttonHeight = 30
        button.setTitle("Button", for: .normal)
        button.setTitleColor(.white, for: .normal)
        button.backgroundColor = .black
        button.layer.cornerRadius = CGFloat(buttonHeight / 2)
        button.translatesAutoresizingMaskIntoConstraints = false
        button.heightAnchor.constraint(equalToConstant: CGFloat(buttonHeight)).isActive = true
        button.translatesAutoresizingMaskIntoConstraints = false
        button.widthAnchor.constraint(equalToConstant: 100).isActive = true
        button.addTarget(self, action: #selector(handleAction), for: .touchUpInside)
        return button
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .systemPink
        configureActionButtonView()
    }
    
    func configureActionButtonView() {
        view.addSubview(actionButton)
        actionButton.translatesAutoresizingMaskIntoConstraints = false
        actionButton.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        actionButton.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
    }
    
    @objc func handleAction() {
        delegateActionButton.didAction(data: "Button Pressed")
    }
}

class SecondChildVC: UIViewController {
    
    private let actionButtonLabel: UILabel = {
        let label = UILabel()
        label.text = "test"
        label.font = .systemFont(ofSize: 18)
        label.textColor = .white
        label.isHidden = true
        return label
    }()
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .systemPurple
        configureActionButtonLabel()
    }
    
    func configureActionButtonLabel() {
        view.addSubview(actionButtonLabel)
        actionButtonLabel.translatesAutoresizingMaskIntoConstraints = false
        actionButtonLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        actionButtonLabel.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
    }
}
extension SecondChildVC: FirstChildVCDelegate {
    func didAction(data: String) {
        actionButtonLabel.isHidden.toggle()
        actionButtonLabel.text = data
    }
}

Initial State

State once Button pressed