Allow transition types to be instantiated and stored on the transitio…

…n controller.

Summary: This makes it possible to configure a transition's behavior.

Reviewers: O2 Material Motion, O4 Material Apple platform reviewers, #material_motion, randcode-generator

Reviewed By: randcode-generator

Tags: #material_motion

Differential Revision: http://codereview.cc/D3199

examples/ContextualTransitionExample.swift

@@ -165,7 +165,7 @@ class PhotoAlbumViewController: UIViewController, UICollectionViewDataSource, UI
 
     super.init(nibName: nil, bundle: nil)
 
-    transitionController.transitionType = PushBackTransition.self
+    transitionController.transition = PushBackTransition()
   }
 
   required init?(coder aDecoder: NSCoder) {
@@ -258,8 +258,6 @@ class PhotoAlbumViewController: UIViewController, UICollectionViewDataSource, UI
 
 private class PushBackTransition: Transition {
 
-  required init() {}
-
   func willBeginTransition(withContext ctx: TransitionContext, runtime: MotionRuntime) -> [Stateful] {
     let foreVC = ctx.fore as! PhotoAlbumViewController
     let foreImageView = (foreVC.collectionView.cellForItem(at: foreVC.indexPathForCurrentPhoto()) as! PhotoCollectionViewCell).imageView

examples/FabTransitionExample.swift

@@ -41,7 +41,7 @@ class FabTransitionExampleViewController: ExampleViewController, TransitionConte
 
   func didTap() {
     let vc = ModalViewController()
-    vc.transitionController.transitionType = CircularRevealTransition.self
+    vc.transitionController.transition = CircularRevealTransition()
     present(vc, animated: true)
   }
 
@@ -76,18 +76,17 @@ private class ModalViewController: UIViewController {
 
 let floodFillOvershootRatio: CGFloat = 1.2
 
-private class CircularRevealTransition: Transition {
+private class CircularRevealTransition: TransitionWithTermination {
 
   // TODO: Support for transient views.
   var floodFillView: UIView!
   var foreViewLayer: CALayer!
-  deinit {
+
+  func didEndTransition(withContext ctx: TransitionContext, runtime: MotionRuntime) {
     floodFillView.removeFromSuperview()
     foreViewLayer.mask = nil
   }
 
-  required init() {}
-
   func willBeginTransition(withContext ctx: TransitionContext, runtime: MotionRuntime) -> [Stateful] {
     foreViewLayer = ctx.fore.view.layer
 

examples/InteractivePushBackTransitionExample.swift

@@ -41,7 +41,7 @@ private class ModalViewController: UIViewController, UIGestureRecognizerDelegate
   override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
     super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
 
-    transitionController.transitionType = PushBackTransition.self
+    transitionController.transition = PushBackTransition()
   }
 
   required init?(coder aDecoder: NSCoder) {
@@ -72,8 +72,6 @@ private class ModalViewController: UIViewController, UIGestureRecognizerDelegate
 
 private class PushBackTransition: Transition {
 
-  required init() {}
-
   func willBeginTransition(withContext ctx: TransitionContext, runtime: MotionRuntime) -> [Stateful] {
     let draggable = Draggable(withFirstGestureIn: ctx.gestureRecognizers)
 

examples/ModalDialogExample.swift

@@ -45,7 +45,7 @@ class ModalDialogViewController: UIViewController {
   override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
     super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
 
-    transitionController.transitionType = ModalDialogTransition.self
+    transitionController.transition = ModalDialogTransition()
     preferredContentSize = .init(width: 200, height: 200)
     modalPresentationStyle = .overCurrentContext
   }
@@ -69,8 +69,6 @@ class ModalDialogViewController: UIViewController {
 
 class ModalDialogTransition: SelfDismissingTransition {
 
-  required init() {}
-
   func willBeginTransition(withContext ctx: TransitionContext, runtime: MotionRuntime) -> [Stateful] {
     let size = ctx.fore.view.frame.size
     let bounds = ctx.containerView().bounds
@@ -106,7 +104,7 @@ class ModalDialogTransition: SelfDismissingTransition {
     return [tossable.spring]
   }
 
-  static func willPresent(fore: UIViewController, dismisser: ViewControllerDismisser) {
+  func willPresent(fore: UIViewController, dismisser: ViewControllerDismisser) {
     let tap = UITapGestureRecognizer()
     fore.view.addGestureRecognizer(tap)
     dismisser.dismissWhenGestureRecognizerBegins(tap)

examples/PushBackTransitionExample.swift

@@ -41,7 +41,7 @@ private class ModalViewController: UIViewController {
   override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
     super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
 
-    transitionController.transitionType = PushBackTransition.self
+    transitionController.transition = PushBackTransition()
   }
 
   required init?(coder aDecoder: NSCoder) {
@@ -67,8 +67,6 @@ private class ModalViewController: UIViewController {
 
 private class PushBackTransition: Transition {
 
-  required init() {}
-
   func willBeginTransition(withContext ctx: TransitionContext, runtime: MotionRuntime) -> [Stateful] {
     let bounds = ctx.containerView().bounds
     let backPosition = bounds.maxY + ctx.fore.view.bounds.height / 2

examples/StickerPickerExample.swift

@@ -108,7 +108,7 @@ private class StickerListViewController: UICollectionViewController {
   init() {
     super.init(collectionViewLayout: UICollectionViewFlowLayout())
 
-    transitionController.transitionType = ModalTransition.self
+    transitionController.transition = ModalTransition()
 
     modalPresentationStyle = .overCurrentContext
   }

src/transitions/Transition.swift

@@ -18,10 +18,10 @@ import Foundation
 import UIKit
 
 /**
- An object that is capable of responding to a transition that is about to begin.
+ A transition is responsible for describing the motion that will occur during a UIViewController
+ transition.
  */
-public protocol WillBeginTransition {
-
+public protocol Transition {
   /**
    Invoked on initiation of a view controller transition.
 
@@ -34,12 +34,11 @@ public protocol WillBeginTransition {
  A transition is responsible for describing the motion that will occur during a UIViewController
  transition.
  */
-public protocol Transition: WillBeginTransition {
-
+public protocol TransitionWithTermination: Transition {
   /**
-   Transitions must be instantiable.
+   Invoked on completion of a view controller transition.
    */
-  init()
+  func didEndTransition(withContext ctx: TransitionContext, runtime: MotionRuntime)
 }
 
 /**
@@ -68,5 +67,5 @@ public protocol TransitionWithPresentation: Transition {
  cause the presented view controller to be dismissed.
  */
 public protocol SelfDismissingTransition: Transition {
-  static func willPresent(fore: UIViewController, dismisser: ViewControllerDismisser)
+  func willPresent(fore: UIViewController, dismisser: ViewControllerDismisser)
 }

src/transitions/TransitionContext.swift

@@ -94,7 +94,7 @@ public final class TransitionContext: NSObject {
 
   weak var delegate: TransitionDelegate?
 
-  init(transitionType: Transition.Type,
+  init(transition: Transition,
        direction: TransitionDirection,
        back: UIViewController,
        fore: UIViewController,
@@ -108,7 +108,7 @@ public final class TransitionContext: NSObject {
     self.window = TransitionTimeWindow(duration: TransitionContext.defaultDuration)
     self.presentationController = presentationController
 
-    self.transition = transitionType.init()
+    self.transition = transition
 
     super.init()
   }
@@ -178,7 +178,7 @@ extension TransitionContext {
 
     var terminators = transition.willBeginTransition(withContext: self, runtime: self.runtime)
 
-    if let presentationController = presentationController as? WillBeginTransition {
+    if let presentationController = presentationController as? Transition {
       terminators.append(contentsOf: presentationController.willBeginTransition(withContext: self,
                                                                                 runtime: self.runtime))
     }
@@ -251,6 +251,10 @@ extension TransitionContext {
     }
     context.completeTransition(completedInOriginalDirection)
 
+    if let transitionWithTermination = transition as? TransitionWithTermination {
+      transitionWithTermination.didEndTransition(withContext: self, runtime: runtime)
+    }
+
     runtime = nil
     transition = nil
 

src/transitions/TransitionController.swift

@@ -63,9 +63,9 @@ public final class TransitionController {
 
    Must be a subclass of MDMTransition.
    */
-  public var transitionType: Transition.Type? {
-    set { _transitioningDelegate.transitionType = newValue }
-    get { return _transitioningDelegate.transitionType }
+  public var transition: Transition? {
+    set { _transitioningDelegate.transition = newValue }
+    get { return _transitioningDelegate.transition }
   }
 
   /**
@@ -164,7 +164,7 @@ private final class TransitioningDelegate: NSObject, UIViewControllerTransitioni
   }
 
   var ctx: TransitionContext?
-  var transitionType: Transition.Type?
+  var transition: Transition?
 
   let dismisser: ViewControllerDismisser
   let gestureDelegate = GestureDelegate()
@@ -183,12 +183,12 @@ private final class TransitioningDelegate: NSObject, UIViewControllerTransitioni
     }
     assert(ctx == nil, "A transition is already active.")
 
-    if let transitionType = transitionType {
-      if direction == .forward, let selfDismissingDirector = transitionType as? SelfDismissingTransition.Type {
+    if let transition = transition {
+      if direction == .forward, let selfDismissingDirector = transition as? SelfDismissingTransition {
         selfDismissingDirector.willPresent(fore: fore, dismisser: dismisser)
       }
 
-      ctx = TransitionContext(transitionType: transitionType,
+      ctx = TransitionContext(transition: transition,
                               direction: direction,
                               back: back,
                               fore: fore,
@@ -245,15 +245,15 @@ private final class TransitioningDelegate: NSObject, UIViewControllerTransitioni
   }
 
   func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
-    guard let transitionWithPresentation = transitionType as? TransitionWithPresentation.Type else {
+    guard let transitionWithPresentation = transition as? TransitionWithPresentation else {
       return nil
     }
     if let presentationController = presentationController {
       return presentationController
     }
-    presentationController = transitionWithPresentation.presentationController(forPresented: presented,
-                                                                               presenting: presenting,
-                                                                               source: source)
+    presentationController = type(of: transitionWithPresentation).presentationController(forPresented: presented,
+                                                                                         presenting: presenting,
+                                                                                         source: source)
     return presentationController
   }
 }