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Yet Another Debug Output (NSLog Replacement)

Posted on November 18, 2008 by John Muchow in Debugging


Although NSlog is convenient for outputting messages to the console, I tire of the date/time and object information that it prints.

As an alternative, one can craft a macro that uses CFShow, which outputs Core Foundation objects to stderr. CFShow uses callbacks to objects to display their descriptions, which allows one to use “%@” like you would when calling NSLog.

I often include the following debug definition as part of my projects:

#define debug(format, ...) CFShow([NSString stringWithFormat:format, ## __VA_ARGS__]);

A few short examples follow showing the difference in output between NSLog and the debug macro shown above.

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struct point
{
  int x;
  int y;
};
typedef struct point POINT;
 
POINT topLeft;
topLeft.x = 15, topLeft.y = 20;
 
NSLog(@"x: %d y: %d", topLeft.x, topLeft.y);
debug(@"x: %d y: %d", topLeft.x, topLeft.y);

The output will now look as follows:

Here’s another example, this time passing in an object:

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NSDate *today = [NSDate date];
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:@"EEEE MMMM d, YYYY"];
NSString *dateString = [dateFormat stringFromDate:today];
[dateFormat release];
 
...
 
NSLog(@"Date: %@", dateString);
debug(@"Date: %@", dateString);

And the corresponding output:

Ahhh, much better.

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