ios - Cannot Zoom UIImageView -

i new swift.

i doing exercise app development book. trying create uiimageview , put image in it, can not zoom image in. there wrong in code, don't know going on.

import uikit  class viewcontroller: uiviewcontroller, uiscrollviewdelegate {       @iboutlet weak var image: uiimageview!     @iboutlet weak var scroll: uiscrollview!      override func viewdidload() {         super.viewdidload()         scroll.delegate = viewcontroller()         updatezoomfor(size:view.bounds.size)         // additional setup after loading view, typically nib.     }      override func didreceivememorywarning() {         super.didreceivememorywarning()         // dispose of resources can recreated.     }      private func viewforzooming(in scrollview: uiscrollview) -> uiimageview{         return image     }      func updatezoomfor(size:cgsize){         let widthscale = size.width / image.bounds.width         let heightscale = size.height / image.bounds.height         let scale = min(widthscale, heightscale)         scroll.minimumzoomscale = scale     }  } 

first, set scroll.delegate = self suggested 3stud1ant3.

second, need match definition of theuiscrollviewdelegate method:

func viewforzooming(in scrollview: uiscrollview) -> uiview? {   return image } 

make sure set zoom scale in updatezoomfor well: scroll.zoomscale = scale.

also need implement this:

override func viewwilllayoutsubviews() {     super.viewwilllayoutsubviews()   updatezoomfor(size: view.bounds.size) }  func scrollviewdidzoom(_ scrollview: uiscrollview) {   updateconstraintsforsize(view.bounds.size) }  fileprivate func updateconstraintsforsize(_ size: cgsize) {    let yoffset = max(0, (size.height - imageview.frame.height) / 2)   imageviewtopconstraint.constant = yoffset   imageviewbottomconstraint.constant = yoffset    let xoffset = max(0, (size.width - imageview.frame.width) / 2)   imageviewleadingconstraint.constant = xoffset   imageviewtrailingconstraint.constant = xoffset    view.layoutifneeded() }