When no gesture recognizer is provided to a gestural interaction that…

… expects one, the interaction now does nothing.

Summary:
Gestural interactions configured to expect a gesture recognizer will no longer connect any streams if a gesture recognizer is not provided.

The `withFirstGestureIn:` now uses this new behavior when it can't find a gesture recognizer that qualifies for the interaction. Prior to this change, if the withFirstGestureIn initializer couldn't find a gesture recognizer it would default to `registerNewRecognizerToTargetView` behavior. This can cause superfluous gesture recognizers to be registered to a view.

Reviewers: O2 Material Motion, O4 Material Apple platform reviewers, #material_motion, markwei

Reviewed By: O2 Material Motion, O4 Material Apple platform reviewers, #material_motion, markwei

Subscribers: markwei

Tags: #material_motion

Differential Revision: http://codereview.cc/D3077

examples/ModalDialogExample.swift

@@ -82,19 +82,20 @@ class ModalDialogTransition: SelfDismissingTransition {
 
     let draggable = Draggable(withFirstGestureIn: ctx.gestureRecognizers)
 
-    let gesture = runtime.get(draggable.nextGestureRecognizer)
     let centerY = ctx.containerView().bounds.height / 2.0
 
     runtime.add(ChangeDirection(withVelocityOf: draggable.nextGestureRecognizer, whenNegative: .forward),
                 to: ctx.direction)
 
-    runtime.connect(gesture
-      .velocityOnReleaseStream()
-      .y()
-      .thresholdRange(min: -100, max: 100)
-      .rewrite([.within: position.y().threshold(centerY).rewrite([.below: .forward,
-                                                                  .above: .backward])]),
-                to: ctx.direction)
+    if let gesture = draggable.nextGestureRecognizer {
+      runtime.connect(runtime.get(gesture)
+        .velocityOnReleaseStream()
+        .y()
+        .thresholdRange(min: -100, max: 100)
+        .rewrite([.within: position.y().threshold(centerY).rewrite([.below: .forward,
+                                                                    .above: .backward])]),
+                  to: ctx.direction)
+    }
 
     let movement = TransitionSpring(back: backPosition,
                                     fore: forePosition,

src/interactions/ChangeDirection.swift

@@ -35,7 +35,7 @@ public final class ChangeDirection: Interaction {
   /**
    The gesture recognizer that will be observed by this interaction.
    */
-  public let gesture: UIPanGestureRecognizer
+  public let gesture: UIPanGestureRecognizer?
 
   /**
    The minimum absolute velocity required change the transition's direction.
@@ -57,7 +57,7 @@ public final class ChangeDirection: Interaction {
   /**
    - parameter minimumVelocity: The minimum absolute velocity required to change the transition's direction.
    */
-  public init(withVelocityOf gesture: UIPanGestureRecognizer, minimumVelocity: CGFloat = 100, whenNegative: TransitionDirection = .backward, whenPositive: TransitionDirection = .backward) {
+  public init(withVelocityOf gesture: UIPanGestureRecognizer?, minimumVelocity: CGFloat = 100, whenNegative: TransitionDirection = .backward, whenPositive: TransitionDirection = .backward) {
     self.gesture = gesture
     self.minimumVelocity = minimumVelocity
     self.whenNegative = whenNegative
@@ -80,6 +80,9 @@ public final class ChangeDirection: Interaction {
   }
 
   public func add(to direction: ReactiveProperty<TransitionDirection>, withRuntime runtime: MotionRuntime, constraints axis: Axis?) {
+    guard let gesture = gesture else {
+      return
+    }
     let axis = axis ?? .y
     let chooseAxis: (MotionObservable<CGPoint>) -> MotionObservable<CGFloat>
     switch axis {

src/interactions/DirectlyManipulable.swift

@@ -64,17 +64,17 @@ public final class DirectlyManipulable: NSObject, Interaction, Togglable, Statef
     for gestureRecognizer in [draggable.nextGestureRecognizer,
                               rotatable.nextGestureRecognizer,
                               scalable.nextGestureRecognizer] {
-                                if gestureRecognizer.delegate == nil {
-                                  gestureRecognizer.delegate = self
+                                if gestureRecognizer?.delegate == nil {
+                                  gestureRecognizer?.delegate = self
                                 }
     }
 
     runtime.connect(enabled, to: draggable.enabled)
     runtime.connect(enabled, to: rotatable.enabled)
     runtime.connect(enabled, to: scalable.enabled)
 
-    let adjustsAnchorPoint = AdjustsAnchorPoint(gestureRecognizers: [rotatable.nextGestureRecognizer,
-                                                                     scalable.nextGestureRecognizer])
+    let anchorPointRecognizers = [rotatable.nextGestureRecognizer, scalable.nextGestureRecognizer].flatMap { $0 }
+    let adjustsAnchorPoint = AdjustsAnchorPoint(gestureRecognizers: anchorPointRecognizers)
     runtime.add(adjustsAnchorPoint, to: view)
 
     aggregateState.observe(state: draggable.state, withRuntime: runtime)

src/interactions/Draggable.swift

@@ -47,7 +47,9 @@ public final class Draggable: Gesturable<UIPanGestureRecognizer>, Interaction, T
                   withRuntime runtime: MotionRuntime,
                   constraints applyConstraints: ConstraintApplicator<CGPoint>? = nil) {
     let reactiveView = runtime.get(view)
-    let gestureRecognizer = dequeueGestureRecognizer(withReactiveView: reactiveView)
+    guard let gestureRecognizer = dequeueGestureRecognizer(withReactiveView: reactiveView) else {
+      return
+    }
     let position = reactiveView.reactiveLayer.position
 
     runtime.connect(enabled, to: ReactiveProperty(initialValue: gestureRecognizer.isEnabled) { enabled in
@@ -75,17 +77,20 @@ public final class Draggable: Gesturable<UIPanGestureRecognizer>, Interaction, T
  CGPoint constraints may be applied to this interaction.
  */
 public final class DraggableFinalVelocity: Interaction {
-  fileprivate init(gestureRecognizer: UIPanGestureRecognizer) {
+  fileprivate init(gestureRecognizer: UIPanGestureRecognizer?) {
     self.gestureRecognizer = gestureRecognizer
   }
 
   public func add(to target: ReactiveProperty<CGPoint>,
                   withRuntime runtime: MotionRuntime,
                   constraints applyConstraints: ConstraintApplicator<CGPoint>? = nil) {
+    guard let gestureRecognizer = gestureRecognizer else {
+      return
+    }
     let gesture = runtime.get(gestureRecognizer)
     runtime.connect(gesture.velocityOnReleaseStream(in: runtime.containerView),
                     to: target)
   }
 
-  let gestureRecognizer: UIPanGestureRecognizer
+  let gestureRecognizer: UIPanGestureRecognizer?
 }

src/interactions/Rotatable.swift

@@ -35,7 +35,9 @@ public final class Rotatable: Gesturable<UIRotationGestureRecognizer>, Interacti
                   withRuntime runtime: MotionRuntime,
                   constraints applyConstraints: ConstraintApplicator<CGFloat>? = nil) {
     let reactiveView = runtime.get(view)
-    let gestureRecognizer = dequeueGestureRecognizer(withReactiveView: reactiveView)
+    guard let gestureRecognizer = dequeueGestureRecognizer(withReactiveView: reactiveView) else {
+      return
+    }
     let rotation = reactiveView.reactiveLayer.rotation
 
     runtime.connect(enabled, to: ReactiveProperty(initialValue: gestureRecognizer.isEnabled) { enabled in

src/interactions/Scalable.swift

@@ -35,7 +35,9 @@ public final class Scalable: Gesturable<UIPinchGestureRecognizer>, Interaction,
                   withRuntime runtime: MotionRuntime,
                   constraints applyConstraints: ConstraintApplicator<CGFloat>? = nil) {
     let reactiveView = runtime.get(view)
-    let gestureRecognizer = dequeueGestureRecognizer(withReactiveView: reactiveView)
+    guard let gestureRecognizer = dequeueGestureRecognizer(withReactiveView: reactiveView) else {
+      return
+    }
     let scale = reactiveView.reactiveLayer.scale
 
     runtime.connect(enabled, to: ReactiveProperty(initialValue: gestureRecognizer.isEnabled) { enabled in

src/interactions/SlopRegion.swift

@@ -29,14 +29,14 @@ public final class SlopRegion: Interaction {
   /**
    The gesture recognizer that will be observed by this interaction.
    */
-  public let gesture: UIPanGestureRecognizer
+  public let gesture: UIPanGestureRecognizer?
 
   /**
    The size of the slop region.
    */
   public let size: CGFloat
 
-  public init(withTranslationOf gesture: UIPanGestureRecognizer, size: CGFloat) {
+  public init(withTranslationOf gesture: UIPanGestureRecognizer?, size: CGFloat) {
     self.gesture = gesture
     self.size = size
   }
@@ -57,6 +57,9 @@ public final class SlopRegion: Interaction {
   }
 
   public func add(to direction: ReactiveProperty<TransitionDirection>, withRuntime runtime: MotionRuntime, constraints axis: Axis?) {
+    guard let gesture = gesture else {
+      return
+    }
     let axis = axis ?? .y
     let chooseAxis: (MotionObservable<CGPoint>) -> MotionObservable<CGFloat>
     switch axis {

src/protocols/Gesturable.swift

@@ -34,11 +34,13 @@ public enum GesturableConfiguration <T: UIGestureRecognizer> {
   case registerNewRecognizerTo(UIView)
 
   /**
-   The interaction will make use of the provided gesture recognizer.
+   The interaction will make use of the provided gesture recognizer, if provided.
+
+   If no gesture recognizer is provided then this interaction will do nothing.
 
    The interaction will not associate this gesture recognizer with any view.
    */
-  case withExistingRecognizer(T)
+  case withExistingRecognizer(T?)
 }
 
 /**
@@ -68,11 +70,7 @@ public class Gesturable<T: UIGestureRecognizer> {
         break
       }
     }
-    if let first = first {
-      self.init(.withExistingRecognizer(first))
-    } else {
-      self.init()
-    }
+    self.init(.withExistingRecognizer(first))
   }
 
   public init(_ config: GesturableConfiguration<T>) {
@@ -81,7 +79,11 @@ public class Gesturable<T: UIGestureRecognizer> {
     let initialState: MotionState
     switch self.config {
     case .withExistingRecognizer(let recognizer):
-      initialState = (recognizer.state == .began || recognizer.state == .changed) ? .active : .atRest
+      if let recognizer = recognizer {
+        initialState = (recognizer.state == .began || recognizer.state == .changed) ? .active : .atRest
+      } else {
+        initialState = .atRest
+      }
     default: ()
       initialState = .atRest
     }
@@ -95,20 +97,21 @@ public class Gesturable<T: UIGestureRecognizer> {
    This property may change after the interaction has been added to a view depending on the
    interaction's configuration.
    */
-  public var nextGestureRecognizer: T {
+  public var nextGestureRecognizer: T? {
     if let nextGestureRecognizer = _nextGestureRecognizer {
       return nextGestureRecognizer
     }
 
-    let gestureRecognizer: T
+    let gestureRecognizer: T?
 
     switch config {
     case .registerNewRecognizerToTargetView:
       gestureRecognizer = T()
 
     case .registerNewRecognizerTo(let view):
-      gestureRecognizer = T()
-      view.addGestureRecognizer(gestureRecognizer)
+      let recognizer = T()
+      view.addGestureRecognizer(recognizer)
+      gestureRecognizer = recognizer
 
     case .withExistingRecognizer(let existingGestureRecognizer):
       gestureRecognizer = existingGestureRecognizer
@@ -121,18 +124,18 @@ public class Gesturable<T: UIGestureRecognizer> {
   /**
    Prepares and returns the gesture recognizer that should be used to drive this interaction.
    */
-  func dequeueGestureRecognizer(withReactiveView reactiveView: ReactiveUIView) -> T {
+  func dequeueGestureRecognizer(withReactiveView reactiveView: ReactiveUIView) -> T? {
     let gestureRecognizer = self.nextGestureRecognizer
     _nextGestureRecognizer = nil
 
     switch config {
     case .registerNewRecognizerToTargetView:
-      reactiveView.view.addGestureRecognizer(gestureRecognizer)
+      reactiveView.view.addGestureRecognizer(gestureRecognizer!)
     default: ()
     }
 
-    gestureRecognizer.view?.isUserInteractionEnabled = true
-    gestureRecognizer.isEnabled = enabled.value
+    gestureRecognizer?.view?.isUserInteractionEnabled = true
+    gestureRecognizer?.isEnabled = enabled.value
 
     return gestureRecognizer
   }