ios - 将闭包作为目标添加到 UIButton

Question

我有一个通用控件类，它需要根据 View Controller 设置按钮的完成。由于 setLeftButtonActionWithClosure 函数需要将闭包作为参数，闭包应该设置为取消按钮的操作。它会怎样在 Swift 中是可能的，因为我们需要将函数名称作为 String 传递给 action: 参数。

func setLeftButtonActionWithClosure(completion: () -> Void)
{
    self.leftButton.addTarget(<#target: AnyObject?#>, action: <#Selector#>, forControlEvents: <#UIControlEvents#>)
}

Answer 1

在 iOS 14 中，Apple 终于将此功能添加到 UIKit。但是，有人可能仍想使用此扩展，因为 Apple 的方法签名不是最优的。

iOS 14:

extension UIControl {
    func addAction(for controlEvents: UIControl.Event = .touchUpInside, _ closure: @escaping()->()) {
        addAction(UIAction { (action: UIAction) in closure() }, for: controlEvents)
    }
}

iOS 14 之前的版本:

extension UIControl {
    func addAction(for controlEvents: UIControl.Event = .touchUpInside, _ closure: @escaping()->()) {
        @objc class ClosureSleeve: NSObject {
            let closure:()->()
            init(_ closure: @escaping()->()) { self.closure = closure }
            @objc func invoke() { closure() }
        }
        let sleeve = ClosureSleeve(closure)
        addTarget(sleeve, action: #selector(ClosureSleeve.invoke), for: controlEvents)
        objc_setAssociatedObject(self, "\(UUID())", sleeve, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)
    }
}

用法:

button.addAction {
    print("Hello, Closure!")
}

或:

button.addAction(for: .touchUpInside) {
    print("Hello, Closure!")
}

或者如果避免保留循环:

self.button.addAction(for: .touchUpInside) { [unowned self] in
    self.doStuff()
}

(此处包含扩展名:https://github.com/aepryus/Acheron)

另请注意，理论上 .primaryActionTriggered 可以替代 .touchUpInside，但它目前似乎在催化剂中存在漏洞，所以我暂时保留它。