iOS版本号

#define IOS5 ([[[UIDevice currentDevice] systemVersion] intValue] >= 5 ? YES : NO)
#define IOS6 ([[[UIDevice currentDevice] systemVersion] intValue] >= 6 ? YES : NO)
#define IOS7 ([[[UIDevice currentDevice] systemVersion] intValue] >= 7 ? YES : NO)
#define IOS8 ([[[UIDevice currentDevice] systemVersion] intValue] >= 8 ? YES : NO)