1、release时，屏蔽log

1. #if defined (DEBUG) && DEBUG == 1  
2.   
3. #else  
4. #define NSLog(...) {};  
5. #endif  

#if defined (DEBUG) && DEBUG == 1

#else
#define NSLog(...) {};
#endif

2、在主线程或在后台执行block

1. #define BACK(block) dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), block)  
2. #define MAIN(block) dispatch_async(dispatch_get_main_queue(),block)  

#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)

3、设备相关

1. #define isRetina ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(640, 960), [[UIScreen mainScreen] currentMode].size) : NO)  
2.   
3. #define iphone5 ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(640, 1136), [[UIScreen mainScreen] currentMode].size) : NO)  
4.   
5. #define isPad (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad)  
6.   
7. #define CurrentSystemVersion ([[UIDevice currentDevice] systemVersion])  
8.   
9. #define CurrentLanguage ([[NSLocale preferredLanguages] objectAtIndex:0])   

#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)

#define CurrentSystemVersion ([[UIDevice currentDevice] systemVersion])

#define CurrentLanguage ([[NSLocale preferredLanguages] objectAtIndex:0]) 

4、区分模拟器和真机

1. #if TARGET_OS_IPHONE  
2. //iPhone Device  
3. #endif  
4.   
5. #if TARGET_IPHONE_SIMULATOR  
6. //iPhone Simulator  
7. #endif  

#if TARGET_OS_IPHONE
//iPhone Device
#endif

#if TARGET_IPHONE_SIMULATOR
//iPhone Simulator
#endif

5、根据是否使用ARC做不同操作

1. #if __has_feature(objc_arc)  
2.     //compiling with ARC  
3. #else  
4.     // compiling without ARC  
5. #endif