In Objective-C, to get the current hour and minute

问题:

I'd like to get the current hour and minute as integers. So if right now is 3:16am, I'd like to get the two integers: 3 and 16.

But it looks like [NSDate date] will give the number of seconds since 1970, or it can give a string of the current time representation, but there is no easy way to get them as integers?

I see a post in Getting current time, but it involved NSDateComponents and NSCalendar? That's way too complicated... all that was need is something like

NSDate *date = [NSDate date];
int hour = [date getHour];     // which is not possible

Is there a simpler way than using 3 classes NSDate, NSDateComponents, and NSCalendar to get the current hour as an integer, or typically, in Objective-C, would we typically still use C language's localtime and tm to get the hour as an integer?

回答1:

NSDate just holds the time that has passed since a certain reference date, to get more meaningful numbers out of this (eg. after taking care of DST, leap years and all the other stupid time stuff), you have to use NSDateComponents with the appropriate NSCalendar.

回答2:

How you interpret the seconds since 1970 depends on the calendar that you are using. There is simply no other option. Fortunately it is not that difficult to set up. See the 'Data and Time Programming Guide' for lots of examples. In your case:

// Assume you have a 'date'
NSCalendar *gregorianCal = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *dateComps = [gregorianCal components: (NSHourCalendarUnit | NSMinuteCalendarUnit)
                                              fromDate: date];
// Then use it
[dateComps minute];
[dateComps hour];

So it really isn't that complicated.

Also note that you could create a 'Class Category' to encapsulate this as:

 @interface NSDate (MyGregorianDateComponents)
  - (NSInteger) getGregorianHour;
  - (NSInteger) getGregorianMinute;
  @end

回答3:

My class can help. https://github.com/TjeerdVurig/Vurig-Calendar/blob/master/Vurig%20Calendar/NSDate%2Bconvenience.m

I'm sure you can figure out the minute part :)