//release屏蔽NSLog
//放在.pch文件里
#ifdef DEBUG
#else
#define NSLog(...) {};
#endif
//G。C。D
#define BACK(block) dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), block)
#define MAIN(block) dispatch_async(dispatch_get_main_queue(),block)
//Device
#define isRetina ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(640, 960), [[UIScreen mainScreen] currentMode].size) : NO)
#define iPhone5 ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(640, 1136), [[UIScreen mainScreen] currentMode].size) : NO)
#define isPad (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad)
//区分模拟器和真机
#if TARGET_OS_IPHONE
//iPhone Device
#endif
#if TARGET_IPHONE_SIMULATOR
//iPhone Simulator
#endif
//ARC
#if __has_feature(objc_arc)
//compiling with ARC
#else
// compiling without ARC
#endif