Question

I’m perplexed as I’m not the method below is seemingly NOT working when looking at my application when both dates are the same Year/Month/Date/Hour/Minute/Sec, HOWEVER when I write a unit test to test it it seems to work fine. Is the code below not robust for some reason?

Code is:

- (BOOL)isAfterThisDate:(NSDate*)thisDate {
    NSComparisonResult result = [self compare:thisDate];
    if (result == NSOrderedDescending) {
        NSLog(@"        - isAfterThisDate: %@ is after %@ is TRUE", [self stringSummary], [thisDate stringSummary]);
        return TRUE;
    } else {
        NSLog(@"        - isAfterThisDate: %@ is after %@ is FALSE", [self stringSummary], [thisDate stringSummary]);
        return FALSE;
    }
}

Here’s an extract from my application log (i.e. when I use this method in my application). I was expecting this to be false like my unit test supports.

isAfterThisDate: Thu 03-11-2011 09:00:00 GMT+10:00 is after Thu 03-11-2011 09:00:00 GMT+10:00 is TRUE

For reference the helper method I used is:

- (NSString*) stringSummary {
    NSDateFormatter* formatter = [[[NSDateFormatter alloc] init] autorelease];
    [formatter setDateFormat:@"EEE dd-MM-yyyy HH:mm:ss zzz"];
    NSString* str = [formatter stringFromDate:self];
    return str;
}

Answer 1

It’s generally better to use

• the highest-level APIs that are available AND
• the most specific API available.

So in this case, -earlierDate: or -laterDate: , if you’re just going to use the resultant date object itself, or if you’re just testing a given date, then yes, -timeIntervalSinceLastDate.

Generally speaking, formatters are only for generating human-readable forms of a value and not for doing operations on the values themselves.