How do I debug with NSLog(@"Inside of the iPhone Simulator")?

Question

I'm used to programming and having log messages be viewable. I know you used to be able to use NSLog() to trace out messages when debugging Cocoa apps. What is the best way to "trace" messages when coding in a iPhone XCode development environment?

Answer 1

NSLog :)

The output is piped to the console window in XCode and the log files on the iPhone (which are viewable through the XCode device manager).

Answer 2

In my project I have a customised solution based on DebugOutput.m This adds the file & line number to the debug output, making it easier to identify where that output text is coming from, while still keeping it brief.

I've augmented the standard solution with a debug mask, so that I can switch debugging on and off for particular areas of functionality in my app. In Debug.h, I have

typedef enum {
kDebugMaskAp- = 1,
kDebugMaskXMLParser = 1 << 1,
kDebugMaskNetwork = 1 << 2,
kDebugMaskAnalytics = 1 << 3,
kDebugMaskCache = 1 << 4,
} debugBitMask;

#define debugForComponent(mask,format,...) if( currentDebugMask() & mask) [[DebugOutput sharedDebug]  output:__FILE__ lineNumber:__LINE__ input:(format), ##__VA_ARGS__]

And in Debug.m

-(void)output:(char*)fileName lineNumber:(int)lineNumber input:(NSString*)input, ...
{
  va_list argList;
  NSString *filePath, *formatStr;

  // Build the path string
  filePath = [[NSString alloc] initWithBytes:fileName length:strlen(fileName) encoding:NSUTF8StringEncoding];

  // Process arguments, resulting in a format string
  va_start(argList, input);
  formatStr = [[NSString alloc] initWithFormat:input arguments:argList];
  va_end(argList);

  // Call NSLog, prepending the filename and line number
  NSLog(@"File:%s Line:%d %@",[((DEBUG_SHOW_FULLPATH) ? filePath : [filePath lastPathComponent]) UTF8String], lineNumber, formatStr);

  [filePath release];
  [formatStr release];
}

In the application, calls look something like this:

debugForComponent(kDebugMaskApp,@"Request failed - error %@", [error localizedDescription]);

Answer 3

I simply use the replace all functionality....

I disable all my NSLog statements by replacing NSLog(@" with //***NSLog(@"

That way I can simply find it (using find in all project files) with //***NSLog(@" and re-enable them

Nothing fancy but it works :)

Answer 4

Here's a great bit of code I picked up somewhere on the web. It defines new functions DLog() and ALog(). DLog messages only appear when the app is compiled with a -DDEBUG flag (define DEBUG). ALog messages ALWAYS appear (even in Release mode).

// DLog is almost a drop-in replacement for NSLog
// DLog();
// DLog(@"here");
// DLog(@"value: %d", x);
// Unfortunately this doesn't work DLog(aStringVariable); you have to do this instead DLog(@"%@", aStringVariable);
#ifdef DEBUG
#       define DLog(fmt, ...) NSLog((@"%s [Line %d] " fmt), __PRETTY_FUNCTION__, __LINE__, ##__VA_ARGS__);
#else
#       define DLog(...)
#endif

// ALog always displays output regardless of the DEBUG setting
#define ALog(fmt, ...) NSLog((@"%s [Line %d] " fmt), __PRETTY_FUNCTION__, __LINE__, ##__VA_ARGS__);