iOS arc和非arc 适用 宏
1:使用宏
+ (void)showAlertWithMessage:(NSString *)messages { dispatch_async(dispatch_get_main_queue(), ^{ UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"版本更新提示" message:messages delegate:nil cancelButtonTitle:@"确定" otherButtonTitles:nil, nil]; [alert show]; #if !__has_feature(objc_arc) [alert release]; #endif }); }
2:使用 ARC helper
#import <Availability.h> #undef ah_retain #undef ah_dealloc #undef ah_autorelease autorelease #undef ah_dealloc dealloc #if __has_feature(objc_arc) #define ah_retain self #define ah_release self #define ah_autorelease self #define ah_dealloc self #else #define ah_retain retain #define ah_release release #define ah_autorelease autorelease #define ah_dealloc dealloc #undef __bridge #define __bridge #undef __bridge_transfer #define __bridge_transfer #endif // Weak reference support #import <Availability.h> #if !__has_feature(objc_arc_weak) #undef ah_weak #define ah_weak unsafe_unretained #undef __ah_weak #define __ah_weak __unsafe_unretained #endif // Weak delegate support #import <Availability.h> #undef ah_weak_delegate #undef __ah_weak_delegate #if __has_feature(objc_arc_weak) && \ (!(defined __MAC_OS_X_VERSION_MIN_REQUIRED) || __MAC_OS_X_VERSION_MIN_REQUIRED >= __MAC_10_8) #define ah_weak_delegate weak #define __ah_weak_delegate __weak #else #define ah_weak_delegate unsafe_unretained #define __ah_weak_delegate __unsafe_unretained #endif