Do I need to disable NSLog before release Application?

One way to do it is to go into your Build settings and under the Debug configuration add a value to "Preprocessor Macros" value like:

DEBUG_MODE=1

Make sure you only do this for the Debug configuration and not for Beta or Release versions. Then in a common header file you can do something like:

#ifdef DEBUG_MODE
#define DLog( s, ... ) NSLog( @"<%p %@:(%d)> %@", self, [[NSString stringWithUTF8String:__FILE__] lastPathComponent], __LINE__, [NSString stringWithFormat:(s), ##__VA_ARGS__] )
#else
#define DLog( s, ... ) 
#endif

Now instead of NSLog use DLog everywhere. When testing and debugging, you'll get debug messages. When you're ready to release a beta or final release, all those DLog lines automatically become empty and nothing gets emitted. This way there's no manual setting of variables or commenting of NSLogs required. Picking your build target takes care of it.

In addition to all the people who wisely commented that not calling NSLog() at all in production runs slightly faster, I'll add that:

All those NSLog() output strings are visible to anyone who downloads your app from the store and runs it with the device plugged into a mac running Xcode (through the Organizer window).

Depending on what information you log (and especially if your app contacts a server, does authentication, etc.), this can be a serious security issue.

Yes, you should disable it. Especially if you're trying to maximize the speed of your code. NSLogging things left and right pollutes the system log that other developers might be trying to dig through and it can have a big impact on speed-critical code (inside loops, etc..) I accidentally left some log messages in a recursive function once and got to release an update with a "30% speed increase!" a few weeks later... ;-)

NSLog is slow and should not be used for release builds. A simple macro like the one below will disable it along with any asserts you might have which should also be disabled. In the less common case where you do want NSLog in a release build, just call it directly. Don't forget to add "-DNDEBUG" to your "other c flags" build settings.

#ifdef NDEBUG
#define MYLog(f, ...) 
#else
#define MYLog(f, ...) NSLog(f, ## __VA_ARGS__)
#endif