How do I get the current date in Cocoa

Question

I'm getting started developing for the iPhone and as such I am looking at different tutorials online as well as trying some different things out myself. Currently, I'm trying to create a countdown until midnight. To get the number of hour, minutes, and seconds, I do the following (which I found somewhere):

NSDate* now = [NSDate date];  int hour = 23 - [[now dateWithCalendarFormat:nil timeZone:nil] hourOfDay]; int min = 59 - [[now dateWithCalendarFormat:nil timeZone:nil] minuteOfHour]; int sec = 59 - [[now dateWithCalendarFormat:nil timeZone:nil] secondOfMinute]; countdownLabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hour, min,sec]; 

However, each place I use -dateWithCalendarFormat:timeZone: I get the following error:

warning: 'NSDate' may not respond to '-dateWithCalendarFormat:timeZone:' (Messages without a matching method signature will be assumed to return 'id' and accept '...' as arguments.) warning: no '-hourOfDay' method found error: invalid operands to binary - (have 'int' and 'id') 

This seems like something very simple. What am I missing?

Also, I've noticed at different places and at different times the asterisk (*) is located either right after the time NSDate* now or right before the variable NSDate *now. What is the difference in the two and why would you use one versus the other?

Answer 1

You have problems with iOS 4.2? Use this Code:

NSDate *currDate = [NSDate date]; NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init]; [dateFormatter setDateFormat:@"dd.MM.YY HH:mm:ss"]; NSString *dateString = [dateFormatter stringFromDate:currDate]; NSLog(@"%@",dateString); 

-->20.01.2011 10:36:02

Answer 2

You must use the following:

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar]; NSDateComponents *dateComponents = [gregorian components:(NSHourCalendarUnit  | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate:yourDateHere]; NSInteger hour = [dateComponents hour]; NSInteger minute = [dateComponents minute]; NSInteger second = [dateComponents second]; [gregorian release]; 

There is no difference between NSDate* now and NSDate *now, it's just a matter of preference. From the compiler perspective, nothing changes.