OK, I am just sick of this... Going to implement the simple Facebook UX

TLYShyNavBar/TLYShyNavBarManager.m

@@ -22,6 +22,8 @@ static inline CGFloat AACStatusBarHeight()
 @interface TLYShyNavBarManager () <UIGestureRecognizerDelegate>
 
 @property (nonatomic, strong) TLYShyViewController *navBarController;
+@property (nonatomic, strong) TLYShyViewController *extensionController;
+
 @property (nonatomic, readwrite) UIView *extensionViewsContainer;
 
 @property (nonatomic) CGFloat previousYOffset;
@@ -57,21 +59,22 @@ static inline CGFloat AACStatusBarHeight()
         self.extensionViewsContainer = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 100.f, 0.f)];
         self.extensionViewsContainer.backgroundColor = [UIColor clearColor];
         
-        TLYShyViewController *extensionController = [[TLYShyViewController alloc] init];
-        extensionController.view = self.extensionViewsContainer;
-        extensionController.contractionAmount = ^(UIView *view)
+        self.extensionController = [[TLYShyViewController alloc] init];
+        self.extensionController.view = self.extensionViewsContainer;
+        self.extensionController.hidesAfterContraction = YES;
+        self.extensionController.contractionAmount = ^(UIView *view)
         {
             return CGRectGetHeight(view.bounds);
         };
         
         __weak typeof(self) weakSelf = self;
-        extensionController.expandedCenter = ^(UIView *view)
+        self.extensionController.expandedCenter = ^(UIView *view)
         {
             return CGPointMake(CGRectGetMidX(view.bounds),
                                CGRectGetMidY(view.bounds) + weakSelf.viewController.topLayoutGuide.length);
         };
         
-        self.navBarController.child = extensionController;
+        self.navBarController.child = self.extensionController;
     }
     return self;
 }
@@ -148,11 +151,9 @@ static inline CGFloat AACStatusBarHeight()
     newContentOffset.y -= deltaY;
     
     [UIView animateWithDuration:fabs(deltaY/contractionVelocity)
-                          delay:0
-                        options:UIViewAnimationOptionCurveLinear
                      animations:^{
                          self.scrollView.contentOffset = newContentOffset;
-                     } completion:nil];
+                     }];
 }
 
 #pragma mark - public methods

TLYShyNavBar/TLYShyViewController.h

@@ -19,22 +19,21 @@ typedef CGFloat(^TLYShyViewControllerContractionAmountBlock)(UIView *view);
  *  triggered. We use this class to control the operations we perform on
  *  the shy view.
  *
- *      ShyViewControllers can have a child, which gets the same offset 
- *  updates as its parent. The use for this is to implement a drawer like
- *  functionality. When a parent is contracted/expanded, we want the child
- *  which is beneath the view to move the same amount so it remains hidden.
+ *      We are making some dangerous assumtions here!!! Most importantly,
+ *  the TLYShyViewController can only be a maximum depth of 2. Adding a
+ *  child to an already childified node is not supported.
  */
 
 @interface TLYShyViewController : NSObject
 
-@property (nonatomic, strong) TLYShyViewController *child;
-
+@property (nonatomic, weak) TLYShyViewController *child;
 @property (nonatomic, weak) UIView *view;
 
 @property (nonatomic, copy) TLYShyViewControllerExpandedCenterBlock expandedCenter;
 @property (nonatomic, copy) TLYShyViewControllerContractionAmountBlock contractionAmount;
 
 @property (nonatomic) BOOL hidesSubviews;
+@property (nonatomic) BOOL hidesAfterContraction;
 
 - (CGFloat)updateYOffset:(CGFloat)deltaY;
 

TLYShyNavBar/TLYShyViewController.m

@@ -12,9 +12,6 @@ const CGFloat contractionVelocity = 40.f;
 
 @interface TLYShyViewController ()
 
-@property (nonatomic, weak) TLYShyViewController *parent;
-@property (nonatomic, readonly) CGFloat parentYOffset;
-
 @property (nonatomic) CGPoint expandedCenterValue;
 @property (nonatomic) CGFloat contractionAmountValue;
 
@@ -24,13 +21,6 @@ const CGFloat contractionVelocity = 40.f;
 
 @implementation TLYShyViewController
 
-- (void)setChild:(TLYShyViewController *)child
-{
-    _child.parent = nil;
-    _child = child;
-    _child.parent = self;
-}
-
 // convenience
 - (CGPoint)expandedCenterValue
 {
@@ -47,47 +37,34 @@ const CGFloat contractionVelocity = 40.f;
     return CGPointMake(self.expandedCenterValue.x, self.expandedCenterValue.y - self.contractionAmountValue);
 }
 
-- (CGFloat)parentYOffset
-{
-    CGFloat parentOffset = 0;
-    if (self.parent)
-    {
-        parentOffset = MIN(0, self.parent.view.center.y - self.parent.expandedCenterValue.y);
-    }
-    
-    return parentOffset;
-}
-
+// This method is courtesy of GTScrollNavigationBar
+// https://github.com/luugiathuy/GTScrollNavigationBar
 - (void)_updateSubviewsToAlpha:(CGFloat)alpha
 {
     for (UIView* view in self.view.subviews)
     {
-        NSString *className = NSStringFromClass([view class]);
-        if (![className isEqualToString:@"_UINavigationBarBackground"] &&
-            ![className isEqualToString:@"_UINavigationBarBackIndicatorView"])
+        bool isBackgroundView = view == self.view.subviews[0];
+        bool isViewHidden = view.hidden || view.alpha < FLT_EPSILON;
+        
+        if (!isBackgroundView && !isViewHidden)
         {
             view.alpha = alpha;
         }
     }
 }
 
-- (CGFloat)_updateYOffsetInternal:(CGFloat)deltaY
+- (CGFloat)updateYOffset:(CGFloat)deltaY
 {
-    CGFloat newYOffset = self.view.center.y + deltaY - self.parentYOffset;
+    if (self.child && deltaY < 0)
+    {
+        deltaY = [self.child updateYOffset:deltaY];
+        self.child.view.hidden = (deltaY) < 0;
+    }
+    
+    CGFloat newYOffset = self.view.center.y + deltaY;
     CGFloat newYCenter = MAX(MIN(self.expandedCenterValue.y, newYOffset), self.contractedCenterValue.y);
     
-    CGFloat residual = newYOffset - newYCenter;
-    
-    if (self.parent && deltaY < 0)
-    {
-        residual = [self.parent _updateYOffsetInternal:residual];
-    }
-    else if (self.child && deltaY > 0)
-    {
-        residual = [self.child _updateYOffsetInternal:residual];
-    }
-    
-    self.view.center = CGPointMake(self.expandedCenterValue.x, newYCenter + self.parentYOffset);
+    self.view.center = CGPointMake(self.expandedCenterValue.x, newYCenter);
     
     if (self.hidesSubviews)
     {
@@ -97,52 +74,30 @@ const CGFloat contractionVelocity = 40.f;
         [self _updateSubviewsToAlpha:newAlpha];
     }
     
+    CGFloat residual = newYOffset - newYCenter;
+    
+    if (self.child && deltaY > 0 && residual > 0)
+    {
+        residual = [self.child updateYOffset:residual];
+        self.child.view.hidden = residual - (newYOffset - newYCenter) > 0;
+    }
+    
     return residual;
 }
 
-- (CGFloat)updateYOffset:(CGFloat)deltaY
-{
-    if (self.child && deltaY < 0)
-    {
-        return [self.child updateYOffset:deltaY];
-    }
-    else
-    {
-        return [self _updateYOffsetInternal:deltaY];
-    }
-}
-
 - (CGFloat)snap:(BOOL)contract afterDelay:(NSTimeInterval)delay
 {
     CGFloat newYCenter = (contract
                           ? self.expandedCenterValue.y - self.contractionAmountValue
                           : self.expandedCenterValue.y);
     
-    CGFloat deltaY = newYCenter - (self.view.center.y - self.parentYOffset);
+    CGFloat deltaY = newYCenter - self.view.center.y;
     CGFloat duration = fabs(deltaY/contractionVelocity);
     
-    if (contract)
-    {
-        CGFloat childDelta = [self.child snap:contract afterDelay:delay];
-        delay += fabs(childDelta/contractionVelocity);
-        
-        deltaY += childDelta;
-    }
-    else
-    {
-        deltaY += [self.child snap:contract afterDelay:delay+duration];
-    }
-    
-    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delay * NSEC_PER_SEC)), dispatch_get_main_queue(), ^
-    {
-        NSLog(@"delay: %.4f", delay);
-        [UIView animateWithDuration:duration
-                              delay:0
-                            options:UIViewAnimationOptionCurveLinear
-                         animations:^{
-                             [self updateYOffset:deltaY];
-                         } completion:nil];
-    });
+    [UIView animateWithDuration:duration
+                     animations:^{
+                         [self updateYOffset:deltaY];
+                     }];
     
     return deltaY;
 }
@@ -164,7 +119,6 @@ const CGFloat contractionVelocity = 40.f;
     {
         [self _updateSubviewsToAlpha:1.f];
     }
-    
     [self.child cleanup];
 }