View transition doesn't animate during custom pop segue - ios

Question

I'm using a custom segue to create an expand animation when I push new view controllers onto my navigation stack. If no sourceRect is specified when prepareForSegue:sender: is called, then the destination view controller is expanded from the center of the source view controller.
ExpandSegue.m:
- (id)initWithIdentifier:(NSString *)identifier source:(UIViewController *)source destination:(UIViewController *)destination {
self = [super initWithIdentifier:identifier source:source destination:destination];
self.sourceRect = CGRectMake(source.view.center.x, source.view.center.y, 0.0, 0.0);
return self;
}
- (void)perform {
UIViewController *sourceViewController = (UIViewController *)self.sourceViewController;
UIViewController *destinationViewController = (UIViewController *)self.destinationViewController;
CGRect destinationRect = sourceViewController.view.frame;
CGFloat tx = self.sourceRect.origin.x + self.sourceRect.size.width/2 - destinationRect.origin.x - destinationRect.size.width/2;
CGFloat ty = self.sourceRect.origin.y + self.sourceRect.size.height/2 - destinationRect.origin.y - destinationRect.size.height/2;
CGFloat sx = self.sourceRect.size.width/destinationRect.size.width;
CGFloat sy = self.sourceRect.size.height/destinationRect.size.height;
[sourceViewController.view addSubview:destinationViewController.view];
[destinationViewController.view setFrame:sourceViewController.view.frame];
[destinationViewController.view setTransform:CGAffineTransformConcat(CGAffineTransformMakeScale(sx, sy), CGAffineTransformMakeTranslation(tx, ty))];
[UIView animateWithDuration:0.5
delay:0.0
options:UIViewAnimationCurveEaseOut
animations:^{
[destinationViewController.view setTransform:CGAffineTransformIdentity];
} completion:^(BOOL finished) {
[destinationViewController.view removeFromSuperview];
[sourceViewController.navigationController pushViewController:destinationViewController animated:NO];
}];
}
The expand segue works as expected. I tried to create a collapse segue by reversing the logic from the expand segue, but this has given me problems. I want the source view controller to shrink down to the size of the destinationRect. If no destinationRect is supplied, then I want the view to shrink to the center of the destination view controller's view.
CollapseSegue.m:
- (id)initWithIdentifier:(NSString *)identifier source:(UIViewController *)source destination:(UIViewController *)destination {
self = [super initWithIdentifier:identifier source:source destination:destination];
self.destinationRect = CGRectMake(source.view.center.x, source.view.center.y, 0.0, 0.0);
return self;
}
- (void)perform {
UIViewController *sourceViewController = (UIViewController *)self.sourceViewController;
UIViewController *destinationViewController = (UIViewController *)self.destinationViewController;
CGRect sourceRect = sourceViewController.view.frame;
CGFloat tx = self.destinationRect.origin.x + self.destinationRect.size.width/2 - sourceRect.origin.x - sourceRect.size.width/2;
CGFloat ty = self.destinationRect.origin.y + self.destinationRect.size.height/2 - sourceRect.origin.y - sourceRect.size.height/2;
CGFloat sx = self.destinationRect.size.width/sourceRect.size.width;
CGFloat sy = self.destinationRect.size.height/sourceRect.size.height;
[sourceViewController.navigationController popViewControllerAnimated:NO];
[destinationViewController.view addSubview:sourceViewController.view];
[sourceViewController.view setFrame:destinationViewController.view.frame];
[UIView animateWithDuration:0.5
delay:0.0
options:UIViewAnimationCurveEaseOut
animations:^{
[sourceViewController.view setTransform:CGAffineTransformConcat(CGAffineTransformMakeScale(sx, sy), CGAffineTransformMakeTranslation(tx, ty))];
} completion:^(BOOL finished) {
[sourceViewController.view removeFromSuperview];
}];
}
Rather than animating nicely, the view for the sourceViewController simply disappears as if I had only called [sourceViewController.navigationController popViewControllerAnimated:NO]; This would seem to indicate that I'm not setting up my view hierarchy properly, but I can't seem to figure out where I'm going wrong! Any help would be greatly appreciated.