使用elementCount和elementAtIndex使UIBezierPath更像NSBezierPath

import UIKit

class CustomUIBezierPath: UIBezierPath {
    var elements: [UIBezierPathElement] = []

    override init() {
        super.init()
    }

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

    override func move(to point: CGPoint) {
        super.move(to: point)
        elements.append(.moveTo(point))
    }

    override func addLine(to point: CGPoint) {
        super.addLine(to: point)
        elements.append(.lineTo(point))
    }

    override func addCurve(to endPoint: CGPoint, controlPoint1: CGPoint, controlPoint2: CGPoint) {
        super.addCurve(to: endPoint, controlPoint1: controlPoint1, controlPoint2: controlPoint2)
        elements.append(.curveTo(endPoint, controlPoint1: controlPoint1, controlPoint2: controlPoint2))
    }

    override func addQuadCurve(to endPoint: CGPoint, controlPoint: CGPoint) {
        super.addQuadCurve(to: endPoint, controlPoint: controlPoint)
        elements.append(.quadCurveTo(endPoint, controlPoint: controlPoint))
    }

    override func close() {
        super.close()
        elements.append(.close)
    }

    func elementCount() -> Int {
        return elements.count
    }

    func elementAtIndex(_ index: Int) -> UIBezierPathElement? {
        if index< elements.count {
            return elements[index]
        }
        return nil
    }
}