Added MotionViewTransition to make transitions of views possible

Motion.xcodeproj/project.pbxproj

@@ -87,6 +87,8 @@
 		96E409AB1F24F7570015A2B5 /* MotionPreprocessor.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E409621F24F7370015A2B5 /* MotionPreprocessor.swift */; settings = {ATTRIBUTES = (Public, ); }; };
 		96E409AC1F24F7570015A2B5 /* SourcePreprocessor.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E409631F24F7370015A2B5 /* SourcePreprocessor.swift */; settings = {ATTRIBUTES = (Public, ); }; };
 		96E409AD1F24F7570015A2B5 /* TransitionPreprocessor.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E409641F24F7370015A2B5 /* TransitionPreprocessor.swift */; settings = {ATTRIBUTES = (Public, ); }; };
+		9D72470D21557F7000C04B48 /* MotionViewTransition.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9D72470C21557F7000C04B48 /* MotionViewTransition.swift */; };
+		9D7247132158A15E00C04B48 /* MotionViewTransitionAnimator.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9D7247122158A15E00C04B48 /* MotionViewTransitionAnimator.swift */; };
 		D4A2ECE521467454003162B4 /* Application.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4A2ECE421467454003162B4 /* Application.swift */; };
 /* End PBXBuildFile section */
 
@@ -137,6 +139,8 @@
 		96E409641F24F7370015A2B5 /* TransitionPreprocessor.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = TransitionPreprocessor.swift; sourceTree = "<group>"; };
 		96E409BB1F24FC210015A2B5 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		96E409BC1F24FC300015A2B5 /* LICENSE */ = {isa = PBXFileReference; lastKnownFileType = text; path = LICENSE; sourceTree = "<group>"; };
+		9D72470C21557F7000C04B48 /* MotionViewTransition.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MotionViewTransition.swift; sourceTree = "<group>"; };
+		9D7247122158A15E00C04B48 /* MotionViewTransitionAnimator.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MotionViewTransitionAnimator.swift; sourceTree = "<group>"; };
 		D4A2ECE421467454003162B4 /* Application.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Application.swift; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
@@ -194,6 +198,7 @@
 				96E4095A1F24F7370015A2B5 /* MotionModifier.swift */,
 				96E4095C1F24F7370015A2B5 /* MotionTargetState.swift */,
 				96E4095B1F24F7370015A2B5 /* MotionTransitionObserver.swift */,
+				9D72470C21557F7000C04B48 /* MotionViewTransition.swift */,
 				96E4093C1F24F7370015A2B5 /* Animator */,
 				96E409431F24F7370015A2B5 /* Extensions */,
 				96E4095D1F24F7370015A2B5 /* Preprocessors */,
@@ -210,6 +215,7 @@
 				96E4093E1F24F7370015A2B5 /* MotionAnimatorViewContext.swift */,
 				96E4093F1F24F7370015A2B5 /* MotionCoreAnimationViewContext.swift */,
 				96E409421F24F7370015A2B5 /* MotionViewPropertyViewContext.swift */,
+				9D7247122158A15E00C04B48 /* MotionViewTransitionAnimator.swift */,
 			);
 			path = Animator;
 			sourceTree = "<group>";
@@ -360,6 +366,7 @@
 				965FE9931FE43DE10098BDD0 /* MotionTransition+UINavigationControllerDelegate.swift in Sources */,
 				96E409861F24F7370015A2B5 /* MotionPreprocessor.swift in Sources */,
 				96E409821F24F7370015A2B5 /* CascadePreprocessor.swift in Sources */,
+				9D7247132158A15E00C04B48 /* MotionViewTransitionAnimator.swift in Sources */,
 				96E4096C1F24F7370015A2B5 /* Motion+CALayer.swift in Sources */,
 				96E409781F24F7370015A2B5 /* MotionCAAnimation.swift in Sources */,
 				96E409811F24F7370015A2B5 /* MotionTargetState.swift in Sources */,
@@ -378,6 +385,7 @@
 				965FE9691FDDA1F20098BDD0 /* MotionViewOrderStrategy.swift in Sources */,
 				965FE97A1FE1D83D0098BDD0 /* MotionTransition.swift in Sources */,
 				965FE98D1FE334E10098BDD0 /* MotionTransition+UIViewControllerTransitioningDelegate.swift in Sources */,
+				9D72470D21557F7000C04B48 /* MotionViewTransition.swift in Sources */,
 				96E409871F24F7370015A2B5 /* SourcePreprocessor.swift in Sources */,
 				965FE9A11FE43EF80098BDD0 /* MotionTransition+CustomTransition.swift in Sources */,
 				96E409701F24F7370015A2B5 /* Motion+UIKit.swift in Sources */,

Sources/Animator/MotionCoreAnimator.swift

@@ -79,7 +79,7 @@ internal class MotionCoreAnimator<T: MotionAnimatorViewContext>: MotionAnimator
    view is appearing.
    */
   func canAnimate(view: UIView, isAppearing: Bool) -> Bool {
-    guard let state = context[view] else {
+    guard let state = targetState(for: view) else {
       return false
     }
     
@@ -176,6 +176,24 @@ internal class MotionCoreAnimator<T: MotionAnimatorViewContext>: MotionAnimator
     
     invalidateCurrentTime()
   }
+  
+  /**
+   Returns MotionTargetState for the given view.
+   - Parameter for view: A UIView.
+   - Returns: A MotionTargetState.
+   */
+  func targetState(for view: UIView) -> MotionTargetState? {
+    return context[view]
+  }
+
+  /**
+   Returns snapshot view for the given view.
+   - Parameter for view: A UIView.
+   - Returns: A snapshot UIView.
+   */
+  func snapshotView(for view: UIView) -> UIView {
+    return context.snapshotView(for: view)
+  }
 }
 
 fileprivate extension MotionCoreAnimator {
@@ -186,7 +204,7 @@ fileprivate extension MotionCoreAnimator {
    view is appearing.
    */
   func createViewContext(view: UIView, isAppearing: Bool) {
-    viewToContexts[view] = T(animator: self, snapshot: context.snapshotView(for: view), targetState: context[view]!, isAppearing: isAppearing)
+    viewToContexts[view] = T(animator: self, snapshot: snapshotView(for: view), targetState: targetState(for: view)!, isAppearing: isAppearing)
   }
 }
 

Sources/Animator/MotionViewTransitionAnimator.swift

+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (C) 2018, Daniel Dahan and CosmicMind, Inc. <http://cosmicmind.com>.
+ * All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+import UIKit
+
+internal class MotionViewTransitionAnimator: MotionCoreAnimator<MotionCoreAnimationViewContext> {
+  /**
+   Returns MotionTargetState for the given view.
+   - Parameter for view: A UIView.
+   - Returns: A MotionTargetState.
+   */
+  override func targetState(for view: UIView) -> MotionTargetState? {
+    guard let modifiers = view.motionModifiers else {
+      return nil
+    }
+    
+    return MotionTargetState(modifiers: modifiers)
+  }
+  
+  /**
+   Returns snapshot view for the given view.
+   - Parameter for view: A UIView.
+   - Returns: A snapshot UIView.
+   */
+  override func snapshotView(for view: UIView) -> UIView {
+    return view
+  }
+}

Sources/MotionViewTransition.swift

+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (C) 2018, Daniel Dahan and CosmicMind, Inc. <http://cosmicmind.com>.
+ * All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+import UIKit
+
+private var MotionViewTransitionKey: UInt8 = 0
+
+public extension UIView {
+  /// The MotionViewTransition instance associated with the view.
+  var motionViewTransition: MotionViewTransition {
+    get {
+      return AssociatedObject.get(base: self, key: &MotionViewTransitionKey) {
+        MotionViewTransition(self)
+      }
+    }
+  }
+}
+
+open class MotionViewTransition {
+  /// A MotionViewTransitionAnimator used during a transition.
+  private let animator = MotionViewTransitionAnimator()
+  
+  /// A UIView whose subviews and itself will be animating during a transition.
+  private weak var container: UIView?
+
+  /// Maximum duration of the animations.
+  open private(set) var totalDuration: TimeInterval = 0
+  
+  /// Progress of the current transition.
+  open private(set) var progress: CGFloat = 0
+  
+  /// A Boolean to control if the models should be updated when animations end.
+  open var shouldUpdateModels: Bool = true
+  
+  /// Current duration of the animations based on totalDuration and progress.
+  private var currentDuration: TimeInterval {
+    return totalDuration * Double(progress)
+  }
+
+  /**
+   An initializer that accepts a container transition view.
+   - Parameter container: A UIView.
+   */
+  fileprivate init(_ container: UIView) {
+    self.container = container
+  }
+
+  /// Prepares the transition animations.
+  open func start() {
+    guard let v = container else {
+      return
+    }
+    
+    totalDuration = animator.animate(fromViews: v.flattenedViewHierarchy, toViews: [])
+    update(0)
+  }
+  
+  /**
+   Updates the elapsed time for the transition.
+   - Parameter progress: the current progress.
+   */
+  open func update(_ progress: CGFloat) {
+    self.progress = progress.clamp(0, 1)
+    animator.seek(to: currentDuration)
+  }
+  
+  /**
+   Cancels the interactive transition by animatin from the current state
+   to the **beginning** state.
+   - Parameter isAnimated: A boolean indicating if the completion is animated.
+   */
+  open func cancel(isAnimated: Bool = true) {
+    end(isAnimated: isAnimated, isReversed: true)
+  }
+  
+  /**
+   Finishes the interactive transition by animating from the current state
+   to the **end** state.
+   - Parameter isAnimated: A Boolean indicating if the completion is animated.
+   */
+  open func finish(isAnimated: Bool = true) {
+    end(isAnimated: isAnimated, isReversed: false)
+  }
+  
+  deinit {
+    clean()
+  }
+}
+
+private extension MotionViewTransition {
+  /**
+   Ends the interactive transition by animating from the current state
+   to the **beginning** or **end** state based on the value of isReversed.
+   - Parameter isAnimated: A Boolean indicating if the completion is animated.
+   - Parameter isReversed: A Boolean indicating the direction of completion.
+   */
+  func end(isAnimated: Bool, isReversed: Bool) {
+    let duration = isAnimated ? currentDuration : isReversed ? 0 : totalDuration
+    
+    /// 0.00001 is to make sure that animator adds the animations on resume.
+    let after = animator.resume(at: abs(duration - 0.00001), isReversed: isReversed)
+    updateModels()
+    if isAnimated {
+      Motion.delay(after, execute: complete)
+    } else {
+      complete()
+    }
+  }
+  
+  /// Finalizes the transition.
+  func complete() {
+    clean()
+    removeAnimations()
+  }
+  
+  /// Resets the transition.
+  func clean() {
+    animator.clean()
+    totalDuration = 0
+    progress = 0
+  }
+}
+
+private extension MotionViewTransition {
+  /// Updates the layers with final values of animations.
+  func updateModels() {
+    guard shouldUpdateModels else {
+      return
+    }
+  
+    walkingThroughAnimations { layer, _, anim in
+      /// bounds.size somehow is directly set on the layer.
+      let toValue = anim.keyPath == "bounds.size" ? layer.bounds.size : anim.toValue
+      layer.setValue(toValue, forKeyPath: anim.keyPath!)
+    }
+  }
+  
+  /// Removes added animations from layers.
+  func removeAnimations() {
+    guard shouldUpdateModels else {
+      return
+    }
+    
+    walkingThroughAnimations { layer, key, _ in
+      layer.removeAnimation(forKey: key)
+    }
+  }
+
+  /**
+   Walks through each layer's animation and executes give closure with
+   CALayer, animation key String, and CABasicAnimation.
+   - Parameter execute: A closure accepting CALayer, String, and CABasicAnimation
+   which is called for each layer's animation.
+   */
+  func walkingThroughAnimations(execute: (CALayer, String, CABasicAnimation) -> Void) {
+    animator.viewToContexts.keys.forEach { v in
+      v.layer.animations.forEach { key, animation in
+        if let anim = animation as? CABasicAnimation {
+          execute(v.layer, key, anim)
+        }
+      }
+    }
+  }
+}