second_bit_composition.swift

final class PulsateViewAnimator: NSObject {

   private weak var view: UIView?

   private var timer: Timer?
   private let breathOutDuration: TimeInterval
   private let holdDuration: TimeInterval
   private let breathInDuration: TimeInterval
   private let pulseScaleIdentity: CGAffineTransform

   init(view: UIView, pulseScale: CGFloat,
        breathOutDuration: TimeInterval,
        holdDuration: TimeInterval,
        breathInDuration: TimeInterval,
        intervalBetweenPulses: TimeInterval)
   {

       self.view = view
       self.breathInDuration = breathInDuration
       self.breathOutDuration = breathOutDuration
       self.holdDuration = holdDuration
       self.pulseScaleIdentity = CGAffineTransform.init(scaleX: pulseScale, y: pulseScale)

       super.init()

       self.timer = Timer.scheduledTimer(timeInterval: intervalBetweenPulses, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
   }

   @objc func timerAction(timer: Timer) {
       UIView.animate(withDuration: self.breathOutDuration, delay: self.holdDuration, options: .curveEaseInOut, animations: {
           self.view?.transform = self.pulseScaleIdentity
       }) { (completed) in
           if (completed) {
               UIView.animate(withDuration: self.breathInDuration, delay: self.holdDuration, options: .curveEaseInOut,
                              animations: {
                               self.view?.transform = CGAffineTransform.identity
                   }, completion: { (_) in })
           }
       }
   }

   deinit {
       self.timer?.invalidate()
       self.view = nil
   }
}