Question

Been watching a WWDC video today about new features in xCode 4. They have mentioned that it a good idea to use log message actions on breakpoints along with “automatically continue after evaluation actions” enabled to output a variable’s value for instance instead of using NSLogs all the time.

lets say I have something like that:

NSLog(@"URL is : %@", userDocumentsURL);

How would I write a log message action to display userDocumentsURL’s value? Is it really a good idea to use the above method instead of NSLog?

Answer 1

Create a Breakpoint ‘Log Message’ action. For the log message include something like:

URL is @(char*) [[userDocumentsURL description] UTF8String]@

Alternatively you can create a breakpoint ‘Debugger command’ action similar to:

po [NSString stringWithFormat:@"URL is: %@", userDocumentsURL]

I prefer using breakpoint actions for logging, as it’s arguably easier to clear out a bunch of breakpoints than it is to remove NSLogs. A possible downside to using breakpoints in this fashion is that they are significantly slower (during debugging) than a direct NSLog.