I have the latest version of Xcode. In one of my projects I noticed that the views for the iPhone were the new iPhone 5 screen sizes. I like it but is there a way to switch back to the smaller screen size? Not everyone has the iPhone 5.
Also, when your building your interface, you'll see a small icon that lets you quickly switch between 4" and 3.5" screens. It's the rectangular icon on the left. It toggles back and forth between phone sizes.
There's a size property in the attributes, so you can choose the pre iPhone5 size of 3.5
Update: It's now under Editor->Simulated Screen. It's combined with orientation (portrait vs. landscape).
You can switch between the Form Factors(IPhone 5 and the previous versions) by clicking on Editor->Apply Form Factor
来源：https://stackoverflow.com/questions/12584376/xcode-storyboard-displaying-the-new-iphone-5-screen-size