How to create Selector with parameters from string

问题

I am writing a program using Swift 3.1 and Xcode 8.3.3. I want to create a class, responsible for moving entire view when keyboard appears and disappears. But I faced difficulties with creating custom Selector with parameters from string. To show or hide keyboard we need function:

func keyboardWillShow(notification: Notification) {
//Code moving view when keyboard appears
}

I am trying to create a selector like this:

let selector = Selector(("keyboardWillShow")
NotificationCenter.default.addObserver(view, selector: selector, name: .UIKeyboardWillShow, object: anyView.view.window)

It is compiling, but when keyboard appears, it crashes. Because it is independent class I cannot use this construction:

#selector(keyboardWillShow)

Because it transforms Swift function to Objective-C function (adding @objc). So question is: how to create a Selector form with parameters string?

P. S. I can put the whole code there but I don't want question to be very big, so I will edit question if somebody asks...

回答1:

Here is what you want, Selector with string type and Notification parameter argument

Swift 4

NotificationCenter.default.addObserver(self, selector: Selector(("showKeyboard:")), name:NSNotification.Name.UIKeyboardWillShow, object: nil)

var keyboardHeight = 0.0
//-------------------
@objc func showKeyboard(_ sender: Notification) {
    keyboardWillShow(sender: sender as NSNotification, adjustHeight: 150)
    print("sender - \(sender)")
}

//-------------------
func keyboardWillShow(sender: NSNotification, adjustHeight: CGFloat) {
    if let keyboardSize = (sender.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
        keyboardHeight = Double(keyboardSize.height)
        // do your calculations
    }
}

Swift 3

NotificationCenter.default.addObserver(view, selector: Selector(("keyboardWillShow:")), name: .UIKeyboardWillShow, object: anyView.view.window)

func keyboardWillShow(_ notification: Notification) { 
       keyboardWillShow(sender: sender as NSNotification, adjustHeight: 150)
        print("sender - \(sender)")

}

Here are normal selector, according to language support
Swift 4

NotificationCenter.default.addObserver(self, selector: #selector(self.showKeyboard(sender:)), name:NSNotification.Name.UIKeyboardWillShow, object: nil)

var keyboardHeight = 0.0

    //-------------------
    @objc func showKeyboard(sender: NSNotification) {
        keyboardWillShow(sender: sender, adjustHeight: 150)
    }

    //-------------------
    func keyboardWillShow(sender: NSNotification, adjustHeight: CGFloat) {
        if let keyboardSize = (sender.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
            keyboardHeight = Double(keyboardSize.height)
            // your operations here
        }
    }

Swift 3

NotificationCenter.default.addObserver(self, selector: #selector(self.showKeyboard(sender:)), name:NSNotification.Name.UIKeyboardWillShow, object: nil)

var keyboardHeight = 0.0

    //-------------------
    func showKeyboard(sender: NSNotification) {
        keyboardWillShow(sender: sender, adjustHeight: 150)
    }

   //-------------------
    func keyboardWillShow(sender: NSNotification, adjustHeight: CGFloat) {
        if let keyboardSize = (sender.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
            keyboardHeight = Double(keyboardSize.height)
            // your operations here
        }
    }

回答2:

This way works,

override func viewDidLoad() {
    super.viewDidLoad()
// put it wherever you want
 NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(showKeyboard), name:UIKeyboardWillShowNotification, object: nil)
}

func showKeyboard(sender: NSNotification) {
    keyboardWillShow(sender, adjustHeight: 150)
}

func keyboardWillShow(sender: NSNotification, adjustHeight: CGFloat) {
    if let keyboardSize = (sender.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.CGRectValue() {
        keyboardHeight = keyboardSize.height
 // do your calculations
    }
}

This will helps you to achieve your expected result.

来源：https://stackoverflow.com/questions/44451683/how-to-create-selector-with-parameters-from-string

标签

ios

swift

notifications

selector

observers