拆分UIViewController子类后UITapGesture无法识别，求解决办法

嘿，我一眼就看出问题出在哪了——你在MyViewController的viewDidLoad里创建的SubclassMyViewController实例是个临时局部对象！执行完setupUserInterface之后，这个子类实例就被系统回收销毁了。而你给logoImage加的手势，target指向的就是这个已经被释放的子类对象，所以点击的时候根本找不到能响应方法的对象，自然没反应。

给你两个可行的解决方案，按需选择：

方案一：让子类自己管理UI和响应逻辑（推荐） #

这种方式更符合单一职责原则，把UI元素和对应的点击逻辑都放在子类里，耦合性更低：

// MyViewController.swift
class MyViewController: UIViewController {
    // 保存子类实例，确保它不会被提前释放
    private let subVC = SubclassMyViewController()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        subVC.setupUserInterface(view: view)
    }
}

// SubclassMyViewController.swift
class SubclassMyViewController: MyViewController {
    func setupUserInterface(view: UIView) {
        view.addSubview(logoImage)
        logoImage.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        logoImage.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
        logoImage.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.5).isActive = true
    }
    
    lazy var logoImage: UIImageView = {
        let imageView = UIImageView()
        imageView.image = UIImage(named: "logo")
        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.contentMode = .scaleAspectFit
        imageView.isUserInteractionEnabled = true
        
        // 手势target指向子类自己，因为doSomething现在在子类里
        let tap = UITapGestureRecognizer(target: self, action: #selector(doSomething))
        imageView.addGestureRecognizer(tap)
        
        return imageView
    }()
    
    @objc func doSomething() {
        log.info("logo was tapped")
    }
}

方案二：如果响应逻辑必须留在父类 #

要是点击后的逻辑必须放在MyViewController里，那你需要让手势的target指向存活的父类实例，同时确保子类实例不被释放：

// MyViewController.swift
class MyViewController: UIViewController {
    private let subVC = SubclassMyViewController()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // 把父类实例传给子类
        subVC.setupUserInterface(view: view, parentVC: self)
    }
    
    @objc func doSomething() {
        log.info("logo was tapped")
    }
}

// SubclassMyViewController.swift
class SubclassMyViewController: MyViewController {
    // 新增参数接收父类实例
    func setupUserInterface(view: UIView, parentVC: MyViewController) {
        view.addSubview(logoImage)
        logoImage.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        logoImage.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
        logoImage.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.5).isActive = true
        
        // 更新手势的target为传入的父类实例
        let tap = UITapGestureRecognizer(target: parentVC, action: #selector(parentVC.doSomething))
        logoImage.addGestureRecognizer(tap)
    }
    
    lazy var logoImage: UIImageView = {
        let imageView = UIImageView()
        imageView.image = UIImage(named: "logo")
        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.contentMode = .scaleAspectFit
        imageView.isUserInteractionEnabled = true
        
        return imageView
    }()
}

关键总结 #

无论选哪种方案，核心都是确保手势的target指向一个没有被释放的对象，同时不要让子类实例成为临时对象被系统回收。方案一更推荐，因为它让代码职责更清晰，后期维护起来也更方便。

内容的提问来源于stack exchange，提问作者Tyrus Rechs