Resize a UIView from only the ends using a UIPanGestureRecognizer - ios

Question

I have a vertical line (UIView) which I need to resize. I currently do it using a pinch gesture but now I need to do it using a swipe gesture and increase or decrease the height from the side I swipe from. So for example, if I swipe down from the TOP END of the line, the line must decrease in size only from the top. The bottom must stay anchored to the original position.
How do I do this?
I also need to be able to move the image around, which I already have implemented using a UIPanGestureRecognizer as well.
Here's what I've playing around with:
I have a small UIView on top end of the vertical line and one on the bottom end of the line. I use these as markers. Now, I'm able to move the top marker up and down. I need to resize the line to the distance between the two markers AND keep the bottom end of the line at the same position as the bottom marker.
This is what I have
func draggedViewForTopMarker(sender: UIPanGestureRecognizer) {
//To move the top marker
var translation = sender.translationInView(self.view)
sender.view!.center = CGPointMake(sender.view!.center.x, sender.view!.center.y + translation.y)
sender.setTranslation(CGPointZero, inView: self.view)
//Find distance between the markers
var distanceBetweenMarkers = (sender.view!.center.y + translation.y) - self.bottomMarker.center.y
print(distanceBetweenMarkers)
if (distanceBetweenMarkers < 0) {
distanceBetweenMarkers = distanceBetweenMarkers*(-1)
}
//**TRYING** to resize the line to have the same height as the distance between the two markers AND make sure its positioned between the markers and the bottom end of the line is still in the same place as it was originally.
var newFrame = CGRectMake(sender.view!.center.x, distanceBetweenMarkers/2, vertical.frame.width, distanceBetweenMarkers)
vertical.frame = newFrame
}
I'm open to different approaches too, or a solution to the problem I have with this approach!
You may check out at Photo Measures Lite on the App Store to better understand what I mean when I say "resize the line from one side only".
Thanks so much!

Answer 1

instead of making a new frame you can just adjust y position of the line to be the same as the top marker, and the height to be the same as the distance between the two markers
func draggedViewForTopMarker(sender: UIPanGestureRecognizer) {
//To move the top marker
var translation = sender.translationInView(self.view)
sender.view!.center = CGPointMake(sender.view!.center.x, sender.view!.center.y + translation.y)
sender.setTranslation(CGPointZero, inView: self.view)
//Find distance between the markers
var distanceBetweenMarkers = self.topMarker.frame.origin.y - self.bottomMarker.frame.origin.y
vertical.frame.origin.y = self.topMarker.frame.origin.y
vertical.frame.size.height = distanceBetweenMarkers
}
But this will only work if the two markers and the vertical line are the subviews of the same superview