xcode storyboard Container View - How do I access the viewcontroller

There is another solution by specifying an identifier for the embed segue(s) and retrieve the corresponding view controllers in method prepareForSegue:

The advantage of this way is that you needn't rely on a specific order in which your child view controllers are added due to the fact that each child view controller is embedded via an unique segue identifier.

Update 2013-01-17 - Example

- (void) prepareForSegue:(UIStoryboardSegue*)segue sender:(id)sender
{
    // -- Master View Controller
    if ([segue.identifier isEqualToString:c_SegueIdEmbedMasterVC])
    {
        self.masterViewController = segue.destinationViewController;
        // ...
    }
    // -- Detail View Controller
    else if ([segue.identifier isEqualToString:c_SegueIdEmbedDetailVC])
    {
        self.detailViewController = segue.destinationViewController;
        // ...
    }
}

c_SegueIdEmbedMasterVC & c_SegueIdEmbedDetailVC are constants with the corresponding ID of the segue IDs defined in the storyboard.

When you add a container view the xcode calls the UIViewController method addChildViewController:

In your case, you can get the container ViewController looking for it on the SplashViewController's list of childViewControllers, something like this:

for (UIViewController *childViewController in [self childViewControllers])
{
    if ([childViewController isKindOfClass:[InstallViewController class]])
    {
        //found container view controller
        InstallViewController *installViewController = (InstallViewController *)childViewController;

        //do something with your container view viewcontroller

        break;
    }
}

I had the same doubt yesterday :)

The answer of Vitor Franchi is correct but could be more performant and convenient. Especially when accessing the child view controller several times.

Create a readonly property

@interface MyViewController ()
@property (nonatomic, weak, readonly) InstallViewController *cachedInstallViewController;
@end

Then create a convenient getter method

- (InstallViewController *)installViewController
{
    if (_cachedInstallViewController) return _cachedInstallViewController;

    __block InstallViewController *blockInstallViewController = nil;
    NSArray *childViewControllers = self.childViewControllers;
    [childViewControllers enumerateObjectsUsingBlock:^(id childViewController, NSUInteger idx, BOOL *stop) {

        if ([childViewController isMemberOfClass:InstallViewController.class])
        {
            blockInstallViewController = childViewController;
            *stop = YES;
        }
    }];

    _cachedInstallViewController = blockInstallViewController;

    return _cachedInstallViewController;
}

From now on access the child view controller that way

[self.installViewController doSomething];