ios - 如何在 swift 中将 touchUpInside 函数作为参数传递？

Question

我创建了一个动态的 UIButton，我想为该按钮动态设置监听器。但是我得到错误:

Use of unresolved identifier 'myFuncName(sender:)'

我的代码(您可以将其粘贴到 Xcode 中并运行):

import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

//        add my button
        let button = Btn()
        button.setListener(buttonTapped)
        view.addSubview(button)
    }

    @objc func buttonTapped() {
        print("tapped")
    }
}

//    -------------------------------
class Btn: UIControl {
    fileprivate let button: UIButton = {
        let swapButton = UIButton()
        let size = CGFloat(50)
        swapButton.frame.size = CGSize(width: size, height: size)
        swapButton.backgroundColor = UIColor.green

        return swapButton
    }()

    override init(frame: CGRect) {
        super.init(frame: frame)
        addSubview(button)
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        addSubview(button)
    }

    func setListener(_ listener: @escaping () -> Void) {
        // Error - Use of unresolved identifier 'listener(sender:)'
        button.addTarget(self, action: #selector(listener(sender:)), for: .touchUpInside)
    }
}

Answer 1

#selector 创建一个指向函数的 Selector。如果您想调用自定义监听器代码块，您需要将其分配给 Btn 的实例变量，然后从私有(private)函数中调用它。

let button = Btn()
button.listener = {
    // your closure here
}

class Btn: UIControl {
    weak var listener: (() -> Void)?

    override init(frame: CGRect) {
        super.init(frame: frame)
        addSubview(button)
        button.addTarget(self, action: #selector(buttonTapped(_:)), for: .touchUpInside)
    }

    @objc private func buttonTapped(_ sender: UIButton) {
        self.listener?()
    }
}