Xcode 4.5 Release Notes

New Features

Editing User Interfaces

• The Interface Builder canvas includes a new button to toggle between iPhone screen layouts. When you click the button, Xcode resizes full-screen views to match the selected iPhone screen size. When the top level views are resized, Xcode uses the resizing rules specified by layout constraints or springs and struts in the size inspector to reflow the contained views. 12290237
  Use this button to toggle between layouts and ensure that the resizing rules you define work as expected on both the new Retina 4 screen and previous screen sizes.

Editing User Interfaces: Storyboards

• Storyboards now support view controller containment. You can add child view controllers to a parent view controller in a storyboard. At runtime, when the viewDidLoad method is called on the parent controller, its view hierarchy (composed of the view hierarchies of its child controllers) is already loaded. 9630246
  To add a view controller as the child of another view controller:
  1. Add a container view from the Object library.
  2. Connect the container view to the child view controller with an embed segue.