iOS判断机型

#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 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)