#define ScreenWidth ([[UIScreen mainScreen] bounds].size.width) #define ScreenHeight ([[UIScreen mainScreen] bounds].size.height) #define iOS8 ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0) #define iOS7 ([[[UIDevice currentDevice] systemVersion] floatValue] >= 7.0) #define iOS6 ([[[UIDevice currentDevice] systemVersion] floatValue] >= 6.0) #define isPad (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad ? YES : NO) #define isPhone (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone ? YES : NO) #define isRetina ([[UIScreen mainScreen] scale] > 1 ? YES : NO)
原文：http://my.oschina.net/qianglong/blog/330163