iOS: #ifdef DEBUG

开发时，经常用到NSLog，但release是又想一次过清掉all NSLog，方法是：在xxx-Prefix.pch里添加

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#ifdef DEBUG

# define DLog(...) NSLog(__VA_ARGS__)

#else

# define DLog(...) /* */

#endif

#define ALog(...) NSLog(__VA_ARGS__)

When you want to log only in debug builds use DLog(). In release builds DLog() will be compiled as an empty comment. Otherwise use ALog() for logging in both debug and release
builds. (A as in always.)

那么"DEBUG"在哪里定义的呢? 在 "Target > Build Settings > Preprocessor Macros > Debug" 里有一个"DEBUG=1"。

当你Run, Test, Analyze时，就属于debug mode，当Profile, Archive时就属于release mode。见你的ios project的"Edit Scheme..."

#ifdef DEBUG的另外一个用处是：用于push notification。sandbox device token and production device token一定不能mix在一起，否则就可能有些device收不到。见/article/8005010.html

因此我们需要为reg device token准备2个url

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#ifdef DEBUG

NSString * const REG_URL=@"http://xxxx/reg_dev_token";

#else

NSString * const REG_URL=@"http://xxxx/reg_production_token";

#endif