Up until now, writing applications that supported previous versions of iOS mostly consisted of updating API calls and minor coding conventions. With iOS 7, Apple has drastically changed the design of all standard UI objects. Knowing the size, position, and layout of all objects for both iOS 7 and previous versions is very important to maintaining a consistent user experience. This is where storyboard previews come in.
In order to use storyboard previews, you must select the assistant editor and navigate to the view you wish to preview (usually a
.storyboard file). Select the Related Files menu option, navigate to Preview, and select the
.storyboard file you wish to preview, as shown in the following screenshot:
You will see an identical preview of your view on the right-hand side of the assistant editor. In the bottom-right corner of the view, you will see a button that says iOS 7.0 and Later. Click on it, and then select iOS 6.1 and Earlier as shown in the following screenshot: