CircleProgressView.swift

import UIKit

class CircleProgressView: UIView {
    var value: CGFloat = 0 {
        didSet {
            DispatchQueue.main.async { [weak self] in
                self?.animate()
            }
        }
    }
    
    private let shapeLayer = CAShapeLayer()
    private let trackLayer = CAShapeLayer()
    private let lineWidth: CGFloat = 20
    
    override func draw(_ rect: CGRect) {
        super.draw(rect)
        
        addShapes()
    }
    
    func addShapes() {
        let circularPath = UIBezierPath(arcCenter: .zero,
                                        radius: frame.width / 2,
                                        startAngle: 0,
                                        endAngle: CGFloat.pi * 2,
                                        clockwise: true)
        trackLayer.path = circularPath.cgPath
        trackLayer.strokeColor = UIColor.gray.cgColor
        trackLayer.lineWidth = lineWidth
        trackLayer.fillColor = UIColor.clear.cgColor
        trackLayer.lineCap = CAShapeLayerLineCap.round
        trackLayer.position = center
        
        shapeLayer.path = circularPath.cgPath
        shapeLayer.strokeColor = UIColor.blue.cgColor
        shapeLayer.lineWidth = lineWidth
        shapeLayer.fillColor = UIColor.clear.cgColor
        shapeLayer.lineCap = .round
        shapeLayer.strokeEnd = 0
        shapeLayer.position = center
        shapeLayer.transform = CATransform3DMakeRotation(-CGFloat.pi / 2, 0, 0, 1)
        
        layer.addSublayer(trackLayer)
        layer.addSublayer(shapeLayer)
    }
    
    func animate() {
        let basicAnimation = CABasicAnimation(keyPath: "strokeEnd")
        basicAnimation.beginTime = CACurrentMediaTime() + 0.1
        basicAnimation.toValue = value
        basicAnimation.duration = 1
        basicAnimation.fillMode = .forwards
        basicAnimation.isRemovedOnCompletion = false
        shapeLayer.add(basicAnimation, forKey: "")
    }
}