NSError *errord;
NSArray *array = [managedObjectContext executeFetchRequest:request
error:&errord];
if (!array) {
    NSLog(@"Error: %@", errord);
    return;
}
NSLog(@"Count of managedObjectContext: %d\n%@", [array count], array);

http://www.cocoabuilder.com/archive/message/cocoa/2007/5/4/182843

Prints content from an NSError or NSArray content from a managedObjectContext.

NSLog with NSError and NSArray with managedObjectContext

debug, osx

Objective C