This is the code for the Container View Controller when setting up a UIContainerView From http://sandmoose.com/post/35714028270/storyboards-with-custom-container-view-controllers

Container View Controller

    #import "ContainerViewController.h"

    #define SegueIdentifierFirst @"embedFirst"
    #define SegueIdentifierSecond @"embedSecond"

    @interface ContainerViewController ()
    @property (strong, nonatomic) NSString *currentSegueIdentifier;
    @end

    @implementation ContainerViewController

    - (void)viewDidLoad
    {
        [super viewDidLoad];

        self.currentSegueIdentifier = SegueIdentifierFirst;
        [self performSegueWithIdentifier:self.currentSegueIdentifier sender:nil];
    }

    - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
    {
        if ([segue.identifier isEqualToString:SegueIdentifierFirst])
        {
            if (self.childViewControllers.count > 0) {
                [self swapFromViewController:[self.childViewControllers objectAtIndex:0] toViewController:segue.destinationViewController];
            }
            else {
                [self addChildViewController:segue.destinationViewController];
                ((UIViewController *)segue.destinationViewController).view.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
                [self.view addSubview:((UIViewController *)segue.destinationViewController).view];
                [segue.destinationViewController didMoveToParentViewController:self];
            }
        }
        else if ([segue.identifier isEqualToString:SegueIdentifierSecond])
        {
            [self swapFromViewController:[self.childViewControllers objectAtIndex:0] toViewController:segue.destinationViewController];
        }
    }

    - (void)swapFromViewController:(UIViewController *)fromViewController toViewController:(UIViewController *)toViewController
    {
        toViewController.view.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);

        [fromViewController willMoveToParentViewController:nil];
        [self addChildViewController:toViewController];
        [self transitionFromViewController:fromViewController toViewController:toViewController duration:1.0 options:UIViewAnimationOptionTransitionCrossDissolve animations:nil completion:^(BOOL finished) {
            [fromViewController removeFromParentViewController];
            [toViewController didMoveToParentViewController:self];
        }];
    }

    - (void)swapViewControllers
    {
        self.currentSegueIdentifier = (self.currentSegueIdentifier == SegueIdentifierFirst) ? SegueIdentifierSecond : SegueIdentifierFirst;
        [self performSegueWithIdentifier:self.currentSegueIdentifier sender:nil];
    }

    @end