swift - Extra CALayer's subLayers in iOS -

i have created new single view project written in swift , print self.view.layer.sublayers.count. number 2, haven't add layer or uiview.

override func viewdidload() {     super.viewdidload()     println(self.view.layer.sublayers.count)     // additional setup after loading view, typically nib. }  override func didreceivememorywarning() {     super.didreceivememorywarning()     // dispose of resources can recreated. } 

i wonder 2 layers are.

every uiview backed calayer, view hierarchy , layer hierarchy connected each other.

if print out subviews, see view has 2 subviews of type _uilayoutguide represent controller's toplayoutguide , bottomlayoutguide. every subview has layer that's 2 sublayers.

to prove it:

override func viewdidload() {     super.viewdidload()      print("top layout guide layer: \((self.toplayoutguide as! uiview).layer)");     print("bottom layout guide layer: \((self.bottomlayoutguide as! uiview).layer)");     print("sublayers: \(self.view.layer.sublayers)"); } 

prints:

top layout guide layer: <calayer: 0x7fef8ac28140> bottom layout guide layer: <calayer: 0x7fef8ac27bc0> sublayers: optional([<calayer: 0x7fef8ac28140>, <calayer: 0x7fef8ac27bc0>])