ios - 在 Swift 中，您如何检测哪些 UIControlEvents 触发了操作？

Question

我目前有 4 个 UITextField 的

@IBOutlet weak var fNameTextField: UITextField!
@IBOutlet weak var lNameTextField: UITextField!
@IBOutlet weak var emailTextField: UITextField!
@IBOutlet weak var phoneTextField: UITextField!

我想跟踪他们的各种事件:

[UIControlEvents.EditingChanged, UIControlEvents.EditingDidBegin, UIControlEvents.EditingDidEnd ]

但我不想有 3 个独立的事件处理程序，所以我创建了一个这样的函数。这个函数很好地告诉我哪个 UITextField 触发了一个事件，但它没有告诉我触发了哪个事件。:

fNameTextField.addTarget(self, action: "onChangeTextField:", forControlEvents: UIControlEvents.AllTouchEvents)
lNameTextField.addTarget(self, action: "onChangeTextField:", forControlEvents: UIControlEvents.AllTouchEvents)
emailTextField.addTarget(self, action: "onChangeTextField:", forControlEvents: UIControlEvents.AllTouchEvents)
phoneTextField.addTarget(self, action: "onChangeTextField:", forControlEvents: UIControlEvents.AllTouchEvents)

func onChangeTextField(sender:UITextField){
    switch(sender){
        case fNameTextField:
            print("First Name")
        case lNameTextField:
            print("Last Name")
        case emailTextField:
            print("E-mail")
        case phoneTextField:
            print("Phone")
        default: break
    }
}

如何打印发件人姓名和触发事件的名称(例如:.EditingDidEnd、.EditingDidEnd、.EditingDidEnd)？

理想情况下，我不想编写多个事件处理程序，我更喜欢一个函数。

像这样:

func onChangeTextField(sender:UITextField){
    switch(sender.eventTriggerd){
        case UIControlEvents.EditingChanged:
            println("EditingChanged")
        case UIControlEvents.EditingDidBegin:
            println("EditingDidBegin")
        case UIControlEvents.EditingDidEnd:
            println("EditingDidEnd")
        default: break
    }
}

Answer 1

不幸的是，您无法区分哪个控制事件触发了 Action 处理程序。这与 Swift 无关；这只是 Cocoa 的一个特性。

这是一个奇怪的设计决定，但事实就是如此。参见，例如，my book ，提示它:

Curiously, none of the action selector parameters provide any way to learn which control event triggered the current action selector call! Thus, for example, to distinguish a Touch Up Inside control event from a Touch Up Outside control event, their corresponding target–action pairs must specify two different action handlers; if you dispatch them to the same action handler, that handler cannot discover which control event occurred.