同时支持ARC和非ARC代码

从https://github.com/ipup/PPRevealSideViewController 里面摘抄出来

以后用到

// define some macros 

#ifndef __has_feature

#define __has_feature(x) 0

#endif

#ifndef __has_extension

#define __has_extension __has_feature // Compatibility with pre-3.0 compilers.

#endif

#if __has_feature(objc_arc) && __clang_major__ >= 3

#define PP_ARC_ENABLED 1

#endif // __has_feature(objc_arc)

#if PP_ARC_ENABLED

#define PP_RETAIN(xx) (xx)

#define PP_RELEASE(xx)  xx = nil

#define PP_AUTORELEASE(xx)  (xx)

#else

#define PP_RETAIN(xx)           [xx retain]

#define PP_RELEASE(xx)          [xx release], xx = nil

#define PP_AUTORELEASE(xx)      [xx autorelease]

#endif

使用

- (void) dealloc {

    self.myLabel = nil;

#if !PP_ARC_ENABLED

    [super dealloc];

#endif

}

UIBarButtonItem *right = [[UIBarButtonItem alloc] initWithTitle:@"Disable NonControlleur bounce"

                                                             style:UIBarButtonItemStylePlain

                                                            target:self

                                                            action:@selector(disableBouncing)];

    self.navigationItem.rightBarButtonItem = PP_AUTORELEASE(right);