问ios中的组动画

EN

class ViewController: UIViewController {
    @IBOutlet weak var loaderView: UIView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        //circularLoader()
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
    }
    
    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()
        drawCircularLoader()
    }
    
    func drawCircularLoader(){
        let width = loaderView.bounds.width
        
        let halfWidth = width / 2
        let size = CGSize(width: halfWidth / 2, height: halfWidth / 2)
        
        let rect = CGRect(x: halfWidth - (size.width / 2), y: (halfWidth / 2) - (size.height / 2), width: size.width, height: size.height)
        
        let path = UIBezierPath(ovalIn: rect)
        let layer = CAShapeLayer()
        
        layer.frame = rect
        layer.fillColor = UIColor.black.cgColor
        
        
        layer.path = path.cgPath
        
        loaderView.layer.addSublayer(layer)
        
        let rotation = CABasicAnimation(keyPath: "transform.rotation")
        rotation.fromValue = 0
        rotation.toValue = 2.0 * .pi
        rotation.duration = 1.5
        layer.add(rotation, forKey: nil)
        
        let scaling = CABasicAnimation(keyPath: "transform.scale")
        scaling.toValue = 1.2
        scaling.duration = 0.3
        scaling.autoreverses = true
        
        let group = CAAnimationGroup()
        group.animations = [rotation, scaling]
        group.repeatCount = .infinity
        layer.add(group, forKey: nil)
        
    }

}