UIViewController Containers Matt Thomas @mthomas codecaffeine.com 

What is a View Controller? 

Model/View/Controller Controller Model View (happy fantasy world) 

Model/View/Controller (reality) Controller Model View Model Controller Controller Controller Controller View View View Controller 

Controller Controller What is a View Controller? Controller View View Controller A Controller coupled to a view 

A View Controller • Manages Views (view property) • Manages Resources (didReceiveMemoryWarning:) • Responds to Events (viewDidRotate:) • Coordinate with Other Controllers View Controller Programming Guide for iOS 

Types of View Controllers • Content View Controllers • Container View Controllers 

Content View Controllers • Basic UIViewController or UITableViewController subclass • The view may be in an associated nib file or created programmatically in the viewController 

Container View Controllers • Manages a Collection of View Controllers • Otherwise just an ordinary View Controller Controller View Controller View Controller View 

Container View Controllers • UINavigationController • UITabBarController • UISplitViewController (iPad only) • UIPageViewController (iOS 5+) examples 

Container View Controllers • Add each view controller’s view to my view • …and forward events… Easy, right? Controller View Controller View Controller View 

Case Study • MGSplitViewController • Wonderful UISplitViewController replacement • https://github.com/mattgemmell/ MGSplitViewController/ 

Case Study - (void)willAnimateFirstHalfOfRotationToInterfaceOrientation: (UIInterfaceOrientation)toInterfaceOrientation duration: (NSTimeInterval)duration { ! [self.masterViewController willAnimateFirstHalfOfRotationToInterfaceOrientation:toInterfaceOrientation duration:duration]; ! [self.detailViewController willAnimateFirstHalfOfRotationToInterfaceOrientation:toInterfaceOrientation duration:duration]; } A lot of code is needed to forward events: 

Events you must implement • viewWillAppear: • viewDidAppear: • viewWillDisappear: • viewDidDisappear: • willRotateToInterfaceOrientation:duration: • didRotateFromInterfaceOrientation: • willAnimateRotationToInterfaceOrientation:duration: • willAnimateFirstHalfOfRotationToInterfaceOrientation:duration: • didAnimateFirstHalfOfRotationToInterfaceOrientation: • willAnimateSecondHalfOfRotationFromInterfaceOrientation:duration: • And don’t forget to call SUPER implementations! (even if you don’t use them in your class) 

iOS 5 to the rescue? • A View Controller can now be added as a child of another View Controller • The events will automatically forward from parent to child Easy, right? 

New UIViewController API • @property childViewControllers • addChildViewController: • removeFromParentViewController • willMoveToParentViewController: • didMoveToParentViewController: • automaticallyForwardAppearanceAndRotationMethodsToChildView Controllers • transitionFromViewController:toViewController:duration:opti ons:animations:completion: 

“A Tale of Two* Hierarchies” *Three if you consider each UIView has a CALayer 

Hierarchy From “Implementing UIViewController Containment” WWDC 2011 

Hierarchy From “Implementing UIViewController Containment” WWDC 2011 

Creating your own Container View Controller 

Why? • iPad has lots of space • Encapsulate Content View Controller 

Half Split View Controller Demo Left ViewController Right ViewController Top ViewController Bottom ViewController 

Tri-Split View Controller Demo Left VC Main View Controller Right VC 

Heck, Combine Them! Left VC Main View Controller Right VC Top ViewController Bottom ViewController 

What did I just create? The apex of UI design :-/ 

Rethinking Container View Controllers (a rant) • “iPad has lots of space” is not a good reason • Easy to go overboard with UI • Best UI isn’t noticeable (iBooks) • Best UI is immersive (Garage Band) • Minimize “Computer Administrative Debris” 

Rethinking Container View Controllers • Container View Controllers are about relationships • Parent-Child (UINavigationController) • Sibling (UITabBarController) • And interactions • Turn Pages (UIPageViewController) 

Card Stack Controller Demo https://github.com/codecaffeine/CardStackController 

Card Stack Controller Demo • Relationship • Each child view controller is atomic • Interaction • Focus on a view controller • See all view controllers 

Implementing container View Controllers • Window must set rootViewController • Requirement for all apps iOS 4+ • rootViewController will be displayed fullscreen • Add children to View Controller hierarchy 

Implementing container View Controllers • Must call didMoveToParentViewController: after addChildViewController: is called and view is added • Must call willMoveToParentViewController: before calling the removeFromParentViewController after view is removed 

Implementing container View Controllers • transitionFromViewController: toViewController: duration: options: animations: completion: • Great for transitioning between two child View Controllers • Will automatically add/remove views to view hierarchy 

Questions?