iOS - NotificationCenter addObserver “UIMenuContro

问题:

I have added notification observer for UIMenuControllerWillHideMenu but it does not call selector added/associated with notification center.

UIMenuControllerWillHideMenu is notification center identifier for UIMenuController and should be called when UIMenuController will hide. But somehow it's not working.

Here is code I've tried (Swift 3.x):

private func addMenuObserverNotification(){
    NotificationCenter.default.addObserver(self, selector: #selector(self.menuControllerWillHideMenu), name: NSNotification.Name(rawValue: "UIMenuControllerWillHideMenu"), object: nil)
}

// This function should be called on 'UIMenuControllerWillHideMenu'
func menuControllerWillHideMenu() -> Void {
    removeMenuObserverNotification()
}


private func removeMenuObserverNotification(){
    NotificationCenter.default.removeObserver(self)
}

Unable to identify, what's wrong.

回答1:

Found a solution by replacing NSNotification.Name(rawValue: "UIMenuControllerWillHideMenu") with just .UIMenuControllerWillHideMenu

private func addMenuObserverNotification(){
    NotificationCenter.default.addObserver(self, selector: #selector(self.menuControllerWillHideMenu), name: .UIMenuControllerWillHideMenu), object: nil)
}

I did a mistake by adding it's initializer NSNotification.Name(rawValue: "UIMenuControllerWillHideMenu"), which may not require as NSNotificationName is typedef NSString, which directly allows an access to predefined values using .<value name>

For more details:
addObserver:selector:name:object:
NSNotificationName