Custom dismissal animation

RootVC.h

@interface RootVC : UIViewController <UIViewControllerTransitioningDelegate>

RootVC.m

#import "TwoStepTransition.h"

- (id <UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed
{
  TwoStepTransition *twoStep = [[TwoStepTransition alloc] init];
  return twoStep;
}

TwoStepTransition.h

#import <Foundation/Foundation.h>

@interface TwoStepTransition : NSObject <UIViewControllerAnimatedTransitioning>

@end

TwoStepTransition.m

@implementation TwoStepTransition

// Just like w/ BouncyTransition

- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext
{
  return 1.0f;
}

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
  // 1. Get the to and from VCs (they're flipped compared to the presentingModal transition)
  UIViewController *toVC = [transitionContext viewControllerForKey:UIViewControllerTransitionContextToViewControllerKey];
  UIViewContorller *fromVC = [transitionContext viewControllerForKey:UIViewControllerTransitionContextFromViewControllerKey];
  // they're also both already in the container view, so no need to add 'em
  
  // 2. Implement keyframe animations
  __block CGRect presentedFrame = [transitionContext initialFrameForViewController:fromVC];
  
  [UIView animatedKeyframesWithDuration:1.0f
    delay:0.0f
    options:0
    animations:^{
      [UIView addKeyframeWithRelativeStartTime:0.0
        relativeDuration:0.8
        animations:^{
          fromVC.view.frame = CGRectMake(
              presentedFrame.origin.x,
              -20,
              presentedFrame.size.width,
              presentedFrame.size.height
              );
      }];
      
      [UIView addKeyframeWithRelativeStartTime:0.8
        relativeDuration:0.2
        animations:^{
          presentedFrame.origin.y += CGRectGetHeight(presentedFrame) + 20;
          fromVC.view.frame = presentedFrame;
          fromVC.view.transform = CGAffineTransformMakeRotation(0.2);
      }];
  } completed:^(BOOL finished) {
      [transitionContext completeTransition:YES];
  }];
  
}