Draw curve

import UIKit
import PlaygroundSupport

extension CGPoint {
    func rect(with radius: CGFloat) -> CGRect {
        return CGRect(x: x - radius, y: y - radius, width: radius * 2, height: radius * 2)
    }
}

class ControlView: UIView {

    private var circle: UIView?
    private let kMargin: CGFloat = 50.0
    private let graphCurve = CAShapeLayer()


    private var controlPoint: CGPoint?

    override init(frame: CGRect) {
        super.init(frame: frame)

        drawLineFromPointToPoint(aX: kMargin, aY: frame.height - kMargin, bX: frame.width - kMargin, bY: kMargin, ofColor: .red, widthOfLine: 13)
        createCircle()
        addAnimation()

    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func drawLineFromPointToPoint(aX: CGFloat, aY: CGFloat, bX: CGFloat, bY: CGFloat, ofColor: UIColor, widthOfLine: CGFloat) {

        let bezier = UIBezierPath()
        bezier.move(to: CGPoint(x: aX, y: aY))
        controlPoint = CGPoint(x: 200, y: 200)
        bezier.addQuadCurve(to: CGPoint(x: bX, y: bY), controlPoint: controlPoint!)

        graphCurve.path = bezier.cgPath
        graphCurve.strokeColor = ofColor.cgColor
        graphCurve.lineWidth = widthOfLine

        graphCurve.fillColor = UIColor.clear.cgColor

        layer.addSublayer(graphCurve)
    }

    func addAnimation() {
        let pathAnimation = CABasicAnimation(keyPath: "strokeEnd")
        pathAnimation.duration = 3
        pathAnimation.fromValue = 0.0
        pathAnimation.toValue = 1
        pathAnimation.fillMode = kCAFillModeForwards
        pathAnimation.isRemovedOnCompletion = false
        pathAnimation.repeatCount = .infinity
        pathAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseIn)
        graphCurve.add(pathAnimation, forKey: "path")

        let followAnimation = CAKeyframeAnimation(keyPath: "position")
        followAnimation.duration = 3
        followAnimation.fillMode = kCAFillModeForwards
        followAnimation.isRemovedOnCompletion = false
        followAnimation.path = graphCurve.path
        followAnimation.repeatCount = .infinity
        followAnimation.calculationMode = kCAAnimationPaced
        followAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseIn)
        circle?.layer.add(followAnimation, forKey: "followPath")
    }

    func createCircle() {
        circle = UIView()

        circle?.backgroundColor = .red
        circle?.frame = CGRect(x: graphCurve.bounds.midX, y: graphCurve.bounds.midY, width: 30, height: 30)

        circle?.layer.cornerRadius = 15
        addSubview(circle!)
    }


}


let view = ControlView(frame: CGRect(x: 0, y: 0, width: 400, height: 250))
view.backgroundColor = .white
PlaygroundPage.current.liveView = view