An extension on CAMediaTimingFunction to enable interoperability with UIViewProtertyAnimator

CAMediaTimingFunction+UITimingCurveProvider.swift

import UIKit
import QuartzCore

//MARK: - NSCopying
extension CAMediaTimingFunction: NSCopying {
  public func copy(with zone: NSZone? = nil) -> Any {
    let c1 = controlPoint1
    let c2 = controlPoint2
    
    return CAMediaTimingFunction(controlPoints: Float(c1.x), Float(c1.y), Float(c2.x), Float(c2.y))
  }
}


//MARK: - UITimingCurveProvider
@available(iOS 10.0, *)
extension CAMediaTimingFunction: UITimingCurveProvider {
  public var timingCurveType: UITimingCurveType {
    return .cubic
  }
  
  public var cubicTimingParameters: UICubicTimingParameters? {
    return UICubicTimingParameters(controlPoint1: controlPoint1, controlPoint2: controlPoint2)
  }
  
  public var springTimingParameters: UISpringTimingParameters? {
    return nil
  }
}


//MARK: - Helpers
fileprivate extension CAMediaTimingFunction {
  var controlPoint1: CGPoint {
    return controlPoint(at: 1)
  }
  
  var controlPoint2: CGPoint {
    return controlPoint(at: 2)
  }
  
  private func controlPoint(at index: Int) -> CGPoint {
    var c: [Float] = [0, 0]
    getControlPoint(at: index, values: &c)
    
    return CGPoint(x: CGFloat(c[0]), y: CGFloat(c[1]))
  }
}


//MARK: - UIViewPropertyAnimator + CAMediaTimingFunction
@available(iOS 10.0, *)
extension UIViewPropertyAnimator {
  convenience init(duration: TimeInterval, timingFunction: CAMediaTimingFunction) {
    self.init(duration: duration, timingParameters: timingFunction)
  }
}