containmentcontroller.m

#import "CYContainerViewController.h"

@implementation CYContainerViewController

- (void)setContainedViewController:(UIViewController * const)aController
{
    [self willChangeValueForKey:@"containedViewController"];
    
    [self.containedViewController willMoveToParentViewController:nil];
    [self.containedViewController removeFromParentViewController];
    [self.containedViewController.view removeFromSuperview];
    [self.containedViewController didMoveToParentViewController:nil];
    
    aController.view.frame            = self.view.bounds;
    aController.view.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
    [aController willMoveToParentViewController:self];
    [self addChildViewController:aController];
    [self.view addSubview:aController.view];
    [aController didMoveToParentViewController:self];
    
    _containedViewController = aController;
    
    [self didChangeValueForKey:@"containedViewController"];
}
@end

@implementation CYContainmentSegue

- (void)perform
{
    NSAssert([self.sourceViewController isKindOfClass:[CYContainerViewController class]],
             @"CYContainmentSegue must be used with a CYContainerViewController.");
    
    CYContainerViewController * const container = self.sourceViewController;
    container.containedViewController = self.destinationViewController;
}
@end