Not sure how to implement "Change the class of a view from UIView to CircularSlider"

Question

I'm trying to use: http://cocoadocs.org/docsets/HGCircularSlider/2.0.0/index.html

Under the "Usage" section, the first step is : "Change the class of a view from UIView to CircularSlider, RangeCircularSlider or MidPointCircularSlider"

I'm not quite sure how to implement this. I've tried the following:

1. My class:

   class TestView: UIView {
       override init (frame : CGRect) {
           super.init(frame : frame)
           let circularSlider = CircularSlider(frame: frame)
           circularSlider.minimumValue = 0.0
           circularSlider.maximumValue = 1.0
           circularSlider.endPointValue = 0.2
           addSubview(circularSlider)
       }
   
       convenience init () {
           self.init(frame:CGRect.zero)
       }
   
       required init(coder aDecoder: NSCoder) {
           fatalError("This class does not support NSCoding")
       }
   }
   

2. In ViewCotroller, under "viewDidLoad":

   let circularSlider = CircularSlider(frame: frame)
   circularSlider.minimumValue = 0.0
   circularSlider.maximumValue = 1.0
   circularSlider.endPointValue = 0.2
   addSubview(circularSlider)
   

Both implementation does show the CircularSlider, but it obvious seems like it's broken. The movement of this circularSlider leaves permanent traces of the circles.

Maybe I'm not correctly implementing: "Change the class of a view from UIView to CircularSlider, RangeCircularSlider or MidPointCircularSlider"