The relationship between AnchorPoint and Position in Layer

I felt difficult to understand the relationship between AnchorPoint and Position in Layer. So I found this in stackoverflow. And it helped me a lot to understand it.

Through my testing I got some principle.

• If a layer’s frame is already defined , the anchorpoint doesn’t affect the position of the layer.

• If you change an anchorPoint of a layer which already has a frame and a position , the origin of the layer’s frame will be changed by the setting of anchorPoint.

  let view = UIView(frame: CGRectMake(0,0,400,400))
  view.backgroundColor = UIColor.grayColor()
  let label1 = UILabel(frame: CGRectMake(100,100,100,20))
  label1.text = "Label1"
  print("AnchorPoint: \(label1.layer.anchorPoint) , Frame: \(label1.layer.frame)")
  print("Position: \(label1.layer.position)")
  label1.backgroundColor = UIColor.whiteColor()
  view.addSubview(label1)
  view
  
  // AnchorPoint to (1,1) 
  
  label1.layer.anchorPoint = CGPoint(x: 1.0, y: 1.0)
  label1.text = "Label1"
  print("AnchorPoint: \(label1.layer.anchorPoint) , Frame: \(label1.layer.frame)")
  view.addSubview(label1)
  view
  

• If you set up a layer’s anchorPoint before you set up the frame of the layer, the position of the layer will be affected by setting of the anchorPoint.

  let label2 = UILabel()
  label2.layer.anchorPoint = CGPoint(x: 1.0, y: 1.0)
  label2.frame = CGRect(origin: CGPoint(x: 100,y: 100), size: CGSize(width: 100.0, height: 20.0))
  print("AnchorPoint: \(label2.layer.anchorPoint) , Frame: \(label2.layer.frame)")
  print("Position: \(label2.layer.position)")
  
  let label3 = UILabel()
  label3.layer.anchorPoint = CGPoint(x: 0.0, y: 0.0)
  label3.frame = CGRect(origin: CGPoint(x: 100, y: 100), size: CGSize(width: 100.0, height: 20.0))
  print("AnchorPoint: \(label3.layer.anchorPoint) , Frame: \(label3.layer.frame)")
  print("Position: \(label3.layer.position)")
  

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