Detecting iPad 3 vs iPad 2?

Question

Possible duplicate:
iPad 2 detection

So, the new version of Xcode has been released with support for iOS 5.1 and the new iPad retina.

I was wondering how you can write code to determine which device it may be, something similar to [[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone so that we can customize our code and projects based on resolution.

Also, what would be the best way to check how your application will look in iPad 3 if you don't have iPad 3?

thanks