转自：http://blog.csdn.net/lvxiangan/article/details/45288505
#define IS_IPAD (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) #define IS_IPHONE (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) #define IS_RETINA ([[UIScreen mainScreen] scale] >= 2.0) #define SCREEN_WIDTH ([[UIScreen mainScreen] bounds].size.width) #define SCREEN_HEIGHT ([[UIScreen mainScreen] bounds].size.height) #define SCREEN_MAX_LENGTH (MAX(SCREEN_WIDTH, SCREEN_HEIGHT)) #define SCREEN_MIN_LENGTH (MIN(SCREEN_WIDTH, SCREEN_HEIGHT)) #define IS_IPHONE_4_OR_LESS (IS_IPHONE && SCREEN_MAX_LENGTH < 568.0) #define IS_IPHONE_5 (IS_IPHONE && SCREEN_MAX_LENGTH == 568.0) #define IS_IPHONE_6 (IS_IPHONE && SCREEN_MAX_LENGTH == 667.0) #define IS_IPHONE_6P (IS_IPHONE && SCREEN_MAX_LENGTH == 736.0)