Modal custom segues in iOS 7.1 give warnings when being dismissed - ios7

Question

Background
I've made a custom segue to allow for "overlay cards" to slide down from the top, and then fly away upon dismissal. When writing the code, I realized that all examples used a UIViewControllerTransitioningDelegate to capture when the segue was animate/dismissed. So far so good, but all examples that I found let the presentingController act as the delegate, which to me sounds strange since I need to "distribute" the logics of how my "overlay card" looks like, in two places; the custom segue, and the presenting controller.
Hence, I figured that I could combine the two into one; the custom segue, which would make my storyboard so much neater, since all view-controllers that I want to show as "overlay cards", simply are assigned the "CardSegue" that I've created, instead of having each and every presenting controller implement UIViewControllerTransitioningDelegate.
Problem
From one of the presenting controllers, I get a warning when dismissing the presented "Overlay card";
UIModalPresentationCustom presentation style can only be used with an animator or with unanimated dismissals.
I looked around, and all I could find was another post that seemed promising;
iOS 7.1 UIModalPresentationCustom warning message
But, the problem is that since my custom segue IS the transitionDelegate, trying to keep it as one logical unit, I can't really apply the reasoning of retaining the delegate...? I mean, the segue is running -- hence, the delegate is alive and well. I'm missing something, or there's an obvious reason that I cannot see right now for why the transitionDelegate MUST be separated from the custom segue?
My code
#define POPUP_MARGIN 25
#interface CardSegue () <UIViewControllerTransitioningDelegate, UIViewControllerAnimatedTransitioning>
#property (nonatomic, assign, getter = isPresenting) BOOL presenting;
#end
#implementation CardSegue
- (void)perform
{
//Make sure that we are the delegate...
[self.destinationViewController setTransitioningDelegate:self];
[self.destinationViewController setModalPresentationStyle:UIModalPresentationCustom];
//Brute-force show the end-result!
[[self sourceViewController] presentViewController:[self destinationViewController] animated:YES completion:nil];
}
#pragma mark - UIViewControllerTransitioningDelegate Methods
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented
presentingController:(UIViewController *)presenting
sourceController:(UIViewController *)source
{
//Configure the animator
self.presenting = YES;
return self;
}
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed
{
self.presenting = NO;
return self;
}
#pragma mark - UIViewControllerContextTransitioning Methods
- (NSTimeInterval)transitionDuration:(id <UIViewControllerContextTransitioning>)transitionContext
{
return 0.5f;
}
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext
{
// Grab the from and to view controllers from the context
UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController *toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
if (self.presenting)
{
// Set our ending frame. We'll modify this later if we have to
CGRect frame = fromViewController.view.frame;
CGRect endFrame = CGRectMake(POPUP_MARGIN, POPUP_MARGIN, frame.size.width - 2 * POPUP_MARGIN, frame.size.height - 2 * POPUP_MARGIN);
fromViewController.view.userInteractionEnabled = NO;
toViewController.view.alpha = 0.0f;
toViewController.view.layer.cornerRadius = 15;
//toViewController.view.layer.borderWidth = 1.5f;
toViewController.view.layer.masksToBounds = YES;
UIView *mainView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, frame.size.width, frame.size.height)];
mainView.backgroundColor = [[UIColor alloc] initWithRed:0.0 green:0.0 blue:0.0 alpha:0.0];
[transitionContext.containerView addSubview:fromViewController.view];
[transitionContext.containerView addSubview:mainView];
[transitionContext.containerView addSubview:toViewController.view];
CGRect startFrame = endFrame;
startFrame.origin.y -= frame.size.height;
toViewController.view.frame = startFrame;
[UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
mainView.backgroundColor = [[UIColor alloc] initWithRed:0.0 green:0.0 blue:0.0 alpha:0.5];
fromViewController.view.tintAdjustmentMode = UIViewTintAdjustmentModeDimmed;
toViewController.view.frame = endFrame;
toViewController.view.alpha = 1.0f;
} completion:^(BOOL finished) {
[transitionContext completeTransition:YES];
}];
}
else {
// Set our ending frame. We'll modify this later if we have to
CGRect frame = toViewController.view.frame;
CGRect endFrame = CGRectMake(POPUP_MARGIN, POPUP_MARGIN, frame.size.width - 2 * POPUP_MARGIN, frame.size.height - 2 * POPUP_MARGIN);
toViewController.view.userInteractionEnabled = YES;
UIView *mainView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, frame.size.width, frame.size.height)];
mainView.backgroundColor = [[UIColor alloc] initWithRed:0.0 green:0.0 blue:0.0 alpha:0.5];
[transitionContext.containerView addSubview:toViewController.view];
[transitionContext.containerView addSubview:mainView];
[transitionContext.containerView addSubview:fromViewController.view];
endFrame.origin.y += frame.size.height;
[UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
toViewController.view.tintAdjustmentMode = UIViewTintAdjustmentModeAutomatic;
mainView.backgroundColor = [[UIColor alloc] initWithRed:0.0 green:0.0 blue:0.0 alpha:0.0];
fromViewController.view.frame = endFrame;
fromViewController.view.alpha = 0.0f;
} completion:^(BOOL finished) {
[transitionContext completeTransition:YES];
}];
}
}
#end