ios - KVO for scroll start & end in UIScrollView -

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is there way use kvo (key value observing) detect scrollviewwillbegindragging , scrollviewdidenddecelerating in swift?

edit: tried 

scrollview.addobserver(self, forkeypath: "dragging", options: nskeyvalueobservingoptions.new, context: nil)

but it's never called. if observe instance "contentoffset" in same way, it's called. kvc compliant?

you can add observers using nsnotification center.

in viewdidload of vc, 

   override func viewdidload() {     super.viewdidload()      nsnotificationcenter.defaultcenter().addobserver(self, selector: #selector(self.informbegindragging), name: "begin", object: nil)     nsnotificationcenter.defaultcenter().addobserver(self, selector: #selector(self.informenddragging), name: "end", object: nil)  }

you can in following 2 methods

    func informbegindragging() {     //do }  func informenddragging() {     //do }

and these 2 methods triggered when scroll view begin dragging or end dragging

    func scrollviewdidenddragging(scrollview: uiscrollview, willdecelerate decelerate: bool) {     nsnotificationcenter.defaultcenter().postnotificationname("end", object: nil) }  func scrollviewwillbegindragging(scrollview: uiscrollview) {     nsnotificationcenter.defaultcenter().postnotificationname("begin", object: nil) }

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