A simple circle drawing/erasing view

CirclesViewController.swift

import UIKit

class ViewController: UIViewController {
    
    lazy var circleLayer: CAShapeLayer = {
        let layer = CAShapeLayer()
        layer.frame = self.circleView.bounds
        
        let bezierPath = UIBezierPath(ovalInRect: layer.bounds)
        self.rotate(bezierPath: bezierPath, degrees: -90.0)
        layer.path = bezierPath.CGPath
        
        layer.lineWidth = 4.0
        layer.strokeColor = UIColor.whiteColor().CGColor
        layer.fillColor = UIColor.clearColor().CGColor
        
        layer.strokeStart = 0
        
        self.circleView.layer.addSublayer(layer)
        return layer
    }()

    @IBOutlet weak var circleView: UIView!
    
    private func rotate(bezierPath path: UIBezierPath, degrees: CGFloat) {
        let box = CGPathGetPathBoundingBox(path.CGPath)
        let translate = CGAffineTransformMakeTranslation(-1 * (box.origin.x + (box.size.width / 2)), -1 * (box.origin.y + (box.size.height / 2)))
        path.applyTransform(translate)
        
        let rotate = CGAffineTransformMakeRotation(degrees * CGFloat(M_PI) / 180)
        path.applyTransform(rotate)
        
        let translateBack = CGAffineTransformMakeTranslation((box.origin.x + (box.size.width / 2)), (box.origin.y + (box.size.height / 2)))
        path.applyTransform(translateBack)
    }
    
    private func drawCircle(from fromValue: CGFloat, to toValue: CGFloat) {
        circleLayer.strokeEnd = toValue
        
        let end = CABasicAnimation(keyPath: "strokeEnd")
        end.fromValue = fromValue
        end.toValue = toValue
        end.duration = 0.2
        circleLayer.addAnimation(end, forKey: nil)
    }
    
    @IBAction func reverseTapped(sender: AnyObject) {
        drawCircle(from: 1, to: 0)
    }
    
    @IBAction func forwardTapped(sender: AnyObject) {
        drawCircle(from: 0, to: 1)
    }
}