QLPreviewController and iOS 3

Can I use 开发者_开发百科QLPreviewController on a device with iOS 3 ?

No this class is only available in iOS 4.0 or higher: http://developer.apple.com/library/iOS/#documentation/NetworkingInternet/Reference/QLPreviewController_Class/Reference/Reference.html

If you go to the documentation, you can see that it is IOS>=4.