title: Draw a line that can stretch like the Xcode assistant editor in Swift
body: <p>When it comes to drawing lines in Swift, most solutions out there are to override the drawRect function in a UIView, but I'm looking for a more dynamic way to draw a line.</p>
  
  <p>I have a button, and I want to be able to drag from this button to the next. While dragging, I would like to draw a line from the starting point to the current touch location (exactly like how the assistant editor in Xcode works, when dragging from one thing to another), but I don't know how to draw a line while I drag from one button to the other.</p>
  
  <p>So my question is: how do I dynamically draw a line from one starting location to the current "touch" location (just like the assistant editor in Xcode)?</p>