Changed to updating model before firing animations

This way we no longer need CAAnimationDelegate to
listen to animationDidStop in order to update the model
and remove animation after it's done. We update the model
in advance, and system just removes the animation on completion

Also fixes animation group not removed from layer after completion

Sources/Extensions/Motion+CALayer.swift

@@ -25,9 +25,6 @@
 
 import UIKit
 
-@available(iOS 10, *)
-extension CALayer: CAAnimationDelegate {}
-
 internal extension CALayer {
   /// Swizzle the `add(_:forKey:) selector.
   internal static var motionAddedAnimations: [(CALayer, String, CAAnimation)]? = {
@@ -110,14 +107,11 @@ public extension CALayer {
    */
   func animate(_ animations: [CAAnimation]) {
     for animation in animations {
-      if nil == animation.delegate {
-        animation.delegate = self
-      }
-      
       if let a = animation as? CABasicAnimation {
         a.fromValue = (presentation() ?? self).value(forKeyPath: a.keyPath!)
       }
       
+      updateModel(animation)
       if let a = animation as? CAPropertyAnimation {
         add(a, forKey: a.keyPath!)
       } else if let a = animation as? CAAnimationGroup {
@@ -129,46 +123,6 @@ public extension CALayer {
   }
   
   /**
-   Executed when an animation has started. 
-   - Parameter _ anim: A CAAnimation.
-   */
-  func animationDidStart(_ anim: CAAnimation) {}
-  
-  /**
-   A delegation function that is executed when the backing layer stops
-   running an animation.
-   - Parameter animation: The CAAnimation instance that stopped running.
-   - Parameter flag: A boolean that indicates if the animation stopped
-   because it was completed or interrupted. True if completed, false
-   if interrupted.
-   */
-  func animationDidStop(_ anim: CAAnimation, finished flag: Bool) {
-    guard let a = anim as? CAPropertyAnimation else {
-      if let a = (anim as? CAAnimationGroup)?.animations {
-        for x in a {
-          animationDidStop(x, finished: true)
-        }
-      }
-      return
-    }
-    
-    guard let b = a as? CABasicAnimation else {
-      return
-    }
-    
-    guard let v = b.toValue else {
-      return
-    }
-    
-    guard let k = b.keyPath else {
-      return
-    }
-    
-    setValue(v, forKeyPath: k)
-    removeAnimation(forKey: k)
-  }
-  
-  /**
    A function that accepts a list of MotionAnimation values and executes them.
    - Parameter animations: A list of MotionAnimation values.
    */
@@ -321,11 +275,7 @@ fileprivate extension CALayer {
         }
       }
       
-      let g = Motion.animate(group: anims, duration: duration)
-      g.fillMode = .both
-      g.isRemovedOnCompletion = false
-      g.timingFunction = ts.timingFunction
-      
+      let g = Motion.animate(group: anims, timingFunction: ts.timingFunction, duration: duration)
       self.animate(g)
       
       if let v = ts.completion {
@@ -338,3 +288,19 @@ fileprivate extension CALayer {
     }
   }
 }
+
+private extension CALayer {
+  /**
+   Updates the model with values provided in animation.
+   - Parameter animation: A CAAnimation.
+  */
+  func updateModel(_ animation: CAAnimation) {
+    if let a = animation as? CABasicAnimation {
+      setValue(a.toValue, forKeyPath: a.keyPath!)
+    } else if let a = animation as? CAAnimationGroup {
+      a.animations?.forEach {
+        updateModel($0)
+      }
+    }
+  }
+}

Sources/Transition/MotionTransition.swift

@@ -207,8 +207,6 @@ extension Motion {
    */
   public class func animate(group animations: [CAAnimation], timingFunction: CAMediaTimingFunction = .easeInOut, duration: CFTimeInterval = 0.5) -> CAAnimationGroup {
     let group = CAAnimationGroup()
-    group.fillMode = .both
-    group.isRemovedOnCompletion = false
     group.animations = animations
     group.duration = duration
     group.timingFunction = timingFunction