reworked the MotionViewPropertyViewContext class

Sources/Animator/MotionDefaultAnimator.swift

@@ -56,6 +56,7 @@ extension MotionDefaultAnimator {
 }
 
 extension MotionDefaultAnimator {
+    /// Cleans the contexts.
     func clean() {
         for v in viewToContexts.values {
             v.clean()
@@ -65,6 +66,12 @@ extension MotionDefaultAnimator {
         insertToViewFirst = false
     }
     
+    /**
+     A function that determines if a view can be animated.
+     - Parameter view: A UIView.
+     - Parameter isAppearing: A boolean that determines whether the
+     view is appearing.
+     */
     func canAnimate(view: UIView, isAppearing: Bool) -> Bool {
         guard let state = context[view] else {
             return false
@@ -73,6 +80,12 @@ extension MotionDefaultAnimator {
         return T.canAnimate(view: view, state: state, isAppearing: isAppearing)
     }
     
+    /**
+     Animates the from-views to the to-views.
+     - Parameter fromViews: An Array of UIViews.
+     - Parameter toViews: An Array of UIViews.
+     - Returns: A TimeInterval.
+     */
     func animate(fromViews: [UIView], toViews: [UIView]) -> TimeInterval {
         var duration: TimeInterval = 0
         
@@ -102,12 +115,23 @@ extension MotionDefaultAnimator {
         return duration
     }
     
+    /**
+     Moves the view's animation to the given elapsed time.
+     - Parameter to elapsedTime: A TimeInterval.
+     */
     func seek(to elapsedTime: TimeInterval) {
         for v in viewToContexts.values {
             v.seek(to: elapsedTime)
         }
     }
     
+    /**
+     Resumes the animation with a given elapsed time and
+     optional reversed boolean.
+     - Parameter at elapsedTime: A TimeInterval.
+     - Parameter isReversed: A boolean to reverse the animation
+     or not.
+     */
     func resume(at elapsedTime: TimeInterval, isReversed: Bool) -> TimeInterval {
         var duration: TimeInterval = 0
         
@@ -119,6 +143,11 @@ extension MotionDefaultAnimator {
         return duration
     }
     
+    /**
+     Applies the given state to the given view.
+     - Parameter state: A MotionTargetState.
+     - Parameter to view: A UIView.
+     */
     func apply(state: MotionTargetState, to view: UIView) {
         guard let v = viewToContexts[view] else {
             return

Sources/Animator/MotionViewPropertyViewContext.swift

@@ -30,38 +30,43 @@ import UIKit
 
 @available(iOS 10, tvOS 10, *)
 internal class MotionViewPropertyViewContext: MotionAnimatorViewContext {
+    /// A reference to the UIViewPropertyAnimator.
+    fileprivate var viewPropertyAnimator: UIViewPropertyAnimator?
+    
+    override class func canAnimate(view: UIView, state: MotionTargetState, isAppearing: Bool) -> Bool {
+        return view is UIVisualEffectView && nil != state.opacity
+    }
 
-  var viewPropertyAnimator: UIViewPropertyAnimator?
-
-  override class func canAnimate(view: UIView, state: MotionTargetState, isAppearing: Bool) -> Bool {
-    return view is UIVisualEffectView && state.opacity != nil
-  }
-
-  override func resume(elapsedTime: TimeInterval, isReversed: Bool) {
-    viewPropertyAnimator?.finishAnimation(at: isReversed ? .start : .end)
-  }
+    override func resume(at elapsedTime: TimeInterval, isReversed: Bool) {
+        viewPropertyAnimator?.finishAnimation(at: isReversed ? .start : .end)
+    }
 
-  override func seek(to elapsedTime: TimeInterval) {
-    viewPropertyAnimator?.pauseAnimation()
-    viewPropertyAnimator?.fractionComplete = CGFloat(elapsedTime / duration)
-  }
+    override func seek(to elapsedTime: TimeInterval) {
+        viewPropertyAnimator?.pauseAnimation()
+        viewPropertyAnimator?.fractionComplete = CGFloat(elapsedTime / duration)
+    }
 
-  override func clean() {
-    super.clean()
-    viewPropertyAnimator?.stopAnimation(true)
-    viewPropertyAnimator = nil
-  }
+    override func clean() {
+        super.clean()
+        viewPropertyAnimator?.stopAnimation(true)
+        viewPropertyAnimator = nil
+    }
 
-  override func startAnimations(isAppearing: Bool) {
-    guard let visualEffectView = snapshot as? UIVisualEffectView else { return }
-    let appearedEffect = visualEffectView.effect
-    let disappearedEffect = targetState.opacity == 0 ? nil : visualEffectView.effect
-    visualEffectView.effect = isAppearing ? disappearedEffect : appearedEffect
+    override func startAnimations(isAppearing: Bool) {
+        guard let v = snapshot as? UIVisualEffectView else {
+            return
+        }
+        
+        let appearedEffect = v.effect
+        let disappearedEffect = 0 == targetState.opacity ? nil : v.effect
+        v.effect = isAppearing ? disappearedEffect : appearedEffect
 
-    duration = targetState.duration!
-    viewPropertyAnimator = UIViewPropertyAnimator(duration: duration, curve: .easeInOut) {
-      visualEffectView.effect = isAppearing ? appearedEffect : disappearedEffect
+        duration = targetState.duration!
+        
+        viewPropertyAnimator = UIViewPropertyAnimator(duration: duration, curve: .easeInOut) {
+            v.effect = isAppearing ? appearedEffect : disappearedEffect
+        }
+        
+        viewPropertyAnimator?.startAnimation()
     }
-    viewPropertyAnimator!.startAnimation()
-  }
 }