带闭包的UIGestureRecognizer

Question

我有视图,我想在其中执行向右滑动手势.不幸的是我收到错误EXC_BAD_ACCESS.有人知道这里有什么问题吗？请看下面的代码.

extension UIView {

    func addGestureRecognizerWithAction(nizer: UIGestureRecognizer, action:() -> ()) {

        class Invoker {
            var action:() -> ()
            init(action:() -> ()) {
                self.action = action
            }
            func invokeTarget(nizer: UIGestureRecognizer) {
                self.action()
                println("Hi from invoker")
            }
        }
        addGestureRecognizer(nizer)
        nizer.addTarget(Invoker(action), action: "invokeTarget:")
    }
}

class BugView: UIView {

    override func awakeFromNib() {
        super.awakeFromNib()

        var swipeRight = UISwipeGestureRecognizer()
        swipeRight.direction = UISwipeGestureRecognizerDirection.Right
        self.addGestureRecognizerWithAction(swipeRight) {
            println("Hi from the gesture closure")
        }
    }
}

Answer 1

恕我直言，这是最简单的解决方案，不需要子类化，因此它非常通用。但它需要关联对象来存储操作：

extension UIGestureRecognizer {

typealias Action = ((UIGestureRecognizer) -> ())

private struct Keys {
    static var actionKey = "ActionKey"
}

private var block: Action? {
    set {
        if let newValue = newValue {
            // Computed properties get stored as associated objects
            withUnsafePointer(to:  &Keys.actionKey) {
                      objc_setAssociatedObject(self, $0, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)
            }
        }
    }
    
    get {
        let action = objc_getAssociatedObject(self, &Keys.actionKey) as? Action
        return action
    }
}

@objc func handleAction(recognizer: UIGestureRecognizer) {
    block?(recognizer)
}

convenience public  init(block: @escaping ((UIGestureRecognizer) -> ())) {
    self.init()
    self.block = block
    self.addTarget(self, action: #selector(handleAction(recognizer:)))
}
}

这允许您甚至对您自己的子类使用以下内容。用法：

    let tapRecognizer = UITapGestureRecognizer { recognizer in
        print("Hallo")
    }
    myView.addGestureRecognizer(tapRecognizer)

编辑：根据 Andrespch 的说法用“withUnsafePointer”更新了此内容。谢谢你的提示。

Answer 2

最后返回true是对的.在上面的回答中,他通过建议制作InvokerNSObject的子类,指出了我正确的方向.

但这不是我在代码中唯一的错误.我发现当滑动发生时,Invoker用于处理事件的对象已经从记忆中消失了.我认为关闭它的提法并没有像它应该的那样被捕获.现在我想出了另一种实现此功能的方法,我想与您分享:

class UIGestureRecognizerWithClosure: NSObject {  // must subclass NSObject otherwise error: "class does not implement methodSignatureForSelector: -- " !!

    var closure:() -> ()

    init(view:UIView, nizer: UIGestureRecognizer, closure:() -> ()) {
        self.closure = closure
        super.init()
        view.addGestureRecognizer(nizer)
        nizer.addTarget(self, action: "invokeTarget:")
    }

    func invokeTarget(nizer: UIGestureRecognizer) {
        self.closure()
    }
}

此代码段显示了如何使用代码:

var swipeRight = UISwipeGestureRecognizer()
swipeRight.direction = UISwipeGestureRecognizerDirection.Right

// swipeWrapper has to be defined as a property: var swipeWrapper:UIGestureRecognizerWithClosure?
// -> this is needed in order to keep the object alive till the swipe event occurs
swipeWrapper = UIGestureRecognizerWithClosure(view: self, nizer:swipeRight) {
    println("Hi from the gesture closure")
}

Answer 3

对于那些不喜欢关联对象和其他棘手东西的人，我有一个小型手势识别器，不需要任何麻烦。而且它不需要存储在某个地方。像常规GR一样工作。尽管它有一些局限性-它是从继承而来的UITapGestureRecognizer，他只知道如何处理水龙头。但是我们经常需要所有的类型吗？我个人不是。

final class BindableGestureRecognizer: UITapGestureRecognizer {
    private var action: () -> Void

    init(action: @escaping () -> Void) {
        self.action = action
        super.init(target: nil, action: nil)
        self.addTarget(self, action: #selector(execute))
    }

    @objc private func execute() {
        action()
    }
}

用法示例：

    let gestureRecognizer = BindableGestureRecognizer {
        print("It's alive!")
    }
    self.view.addGestureRecognizer(gestureRecognizer)

如果出现了一些更有意义的行，请不要忘记[弱自我]。我们不想创建那些不死伙伴。

    let colorGestureRecognizer = BindableGestureRecognizer { [weak self] in
        self?.view.backgroundColor = .red
    }
    self.view.addGestureRecognizer(colorGestureRecognizer)

对我来说似乎很方便，可以从这些@objc衬里中净化我们的视图控制器，并变得更多一点。