Objective-C Fundamentals

Understanding NSLog
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Figure 14.3 The Devices console section of the Organizer window shows log messages not only from
your application’s NSLog calls but also from other system applications and iOS platform services.
Scrolling through the console, you should be able to find the log entries produced by
DebugSample’s calls to NSLog while the device was disconnected from the computer.
While connected, if you launch the application on your device, you should even
notice that the console window updates in real time.
Although it can be handy during development to log a large amount of content via
NSLog, it’s often less than desirable in builds which customers will obtain. Instead of
manually commenting out unnecessary calls to NSLog, you can use some C preprocessor
magic to automatically ensure calls to NSLog appear only in debug builds. Open the
DebugSample_Prefix.pch file and insert the contents shown in the following listing.
Listing 14.2
Helpful macros that improve logging flexibility during development
#ifdef DEBUG
# define LogDebug(...) NSLog(__VA_ARGS__)
#else
# define LogDebug(...) do {} while (0)
#endif
#define LogAlways(...) NSLog(__VA_ARGS__)