Question #15.1 works well in main, but doesn't in category implementation

[clp274]

If I am in main and say I create 2 NSDate objects:
NSDate *currentDate = [NSDate date];
NSDate *anotherDate = [NSDate dateWithNaturalLanguageString:@"January 15, 2012"];

I then proceed to retrieve the day difference result and store it in a unsigned long variable:
NSDateComponents *comps = [cal components:NSDayCalendarUnit fromDate:currentDate toDate:anotherDate options:0];
long days = [coppa day];

I then run NSLog:
NSLog(@"%li", days);

The aforementioned code works exactly as it should.

However, if I put that code in -(unsigned long) elapsedDays: (NSDate *) theDate :

#import "ElapsedDays.h"

@implementation NSDate (ElapsedDays)
-(unsigned long) elapsedDays: (NSDate *) theDate
{
    // Initialize NSCalendar object
    NSCalendar *cal = [[NSCalendar alloc] init];
    // Create variable to store NSDateComponent result returned from components:... method.
    NSDateComponents *comps = [cal components:NSDayCalendarUnit fromDate:self toDate:theDate options:0];
    // Retrieve the long variable day from the datecomponent, which should be the difference between the two dates
    unsigned long elapsedDays = [comps day];
   
    return elapsedDays;
}

@end

When I try to use the that method and run NSLog I get 0. I'm not sure why that is. The only thing I did different I believe was use self for the startdate in the components method. Also, as a follow up question, what should I release to ensure their aren't any memry leaks. Since I allocated NSCalendar, I presume I would have to release that at the end. However, if I try to use dealloc, it doesn't recognize cal NSCalendar object.

[skochan]

Try initializing your calendar using the initWithCalendarIdentifier: method.  You're not supposed to do just an init on it.

The calendar object cal should be released in your elpasedDays: method after you're done using it.

Cheers,

Steve