When creating a storyboard file in Xcode, you must select if it is for iPhone or iPad. This implies one should always put iPhone and iPad UIs into separate storyboards. Is this true?
My app has multiple storyboards. While the Main.storyboard files largely differ between iPhone and iPad, other storyboards are nearly identical. The only difference might be segue being a push on iPhone vs popover on iPad, which can be handled programmatically. It seems awfully silly and redundant to make two storyboards.
So if making one "universal" storyboard, should iPhone or iPad be selected in Xcode? Does it matter?
As of Xcode 6, we can create a single unified storyboard for all the devices. For more info - Documentation
iOS 8 makes dealing with screen size and orientation much more versatile. It is easier than ever to create a single interface for your app that works well on both iPad and iPhone, adjusting to orientation changes and different screen sizes as needed. Design apps with a common interface and then customize them for different size classes. Adapt your user interface to the strengths of each form factor. You no longer need to create a specific iPad storyboard; instead target the appropriate size classes and tune your interface for the best experience.
There are two types of size classes in iOS 8: regular and compact. A regular size class denotes either a large amount of screen space, such as on an iPad, or a commonly adopted paradigm that provides the illusion of a large amount of screen space, such as scrolling on an iPhone. Every device is defined by a size class, both vertically and horizontally. iPad size classes shows the native size classes for the iPad. With the amount of screen space available, the iPad has a regular size class in the vertical and horizontal directions in both portrait and landscape orientations.
Edit: It only supports iOS 8(backward compatible applies only for iOS 7) and later.