Helper methods to control CALayer i.e Interactive transitions

CALayerExtension.swift

import Foundation

extension CALayer {

  func pause() -> TimeInterval {
    if #available(iOS 11, *) {
      let pausedTime = convertTime(CACurrentMediaTime(), from: nil)
      speed = 0
      timeOffset = pausedTime
      return pausedTime
    }
    speed = 0
    return timeOffset
  }
  
  func resume(from pauseTime: TimeInterval? = nil) {
    let pausedTime = pauseTime ?? timeOffset
    speed = 1
    timeOffset = 0
    beginTime = 0
    let timeSincePause = convertTime(CACurrentMediaTime(), from: nil) - pausedTime
    beginTime = timeSincePause
  }
  
  func rewind(finishTime: Double) {
    speed = -1
    if #available(iOS 11, *) {
      beginTime = CACurrentMediaTime()
      DispatchQueue.main.asyncAfter(deadline: .now() + finishTime) {
        self.speed = 1
      }
    }
  }
}