为什么 UIButton removeTarget:action:forControlEvents: 已删除所有目标？

Question

我已将多个目标添加到 UIButton。我想删除其中一个目标，但在 removeTarget:action:forControlEvents: 之后得到了 nil。

import UIKit

class IndexViewController: UIViewController {
    lazy var sndBtn = UIButton(type: .system)

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        view.addSubview(sndBtn)
        sndBtn.setTitle("Hi", for: .normal)

        sndBtn.addTarget(self, action: #selector(IndexViewController.onClick1(_:)), for: .touchUpInside)
        sndBtn.addTarget(self, action: #selector(IndexViewController.onClick2(_:)), for: .touchUpInside)
        print(sndBtn.actions(forTarget: self, forControlEvent: .touchUpInside) as Any)

        sndBtn.removeTarget(self, action: #selector(IndexViewController.onClick1(_:)), for: .touchUpInside)
        print(sndBtn.actions(forTarget: self, forControlEvent: .touchUpInside) as Any)
    }

    @objc
    func onClick1(_ btn: UIButton) {
        print("Method1")
    }

    @objc
    func onClick2(_ btn: UIButton) {
        print("Method2")
    }
}

结果只是显示：

Optional(["onClick1:", "onClick2:"])

nil

Answer 1

根据Apple Docs：

停止传递事件时不考虑 action 参数