NSDate -dateWithNaturalLanguageString: on iPhone?

Question

In the iPhone docset for NSDate, in the discussion area they discuss -dateWithNaturalLanguageString:locale:, however they don't document the method elsewhere on the page.

I've used the method before for iPhone and it worked just fine, although I got warnings. Now that I'm building with -Werror (which I should have been doing all along ^_^) I've run into a warning with this.

How would I replace the following lines of code?

NSDate *today = [NSDate dateWithNaturalLanguageString:@"today at 23:59:59"];
NSDate *tomorrow = [NSDate dateWithNaturalLanguageString:@"tomorrow at 23:59:59"];

Answer 1

One way to do this is with NSCalendar and NSDateComponents.

To get today at 23:59:59:

NSDate *now = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];

NSDateComponents *comps = [calendar components:NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit 
                                      fromDate:date];

[comps setHour:23];
[comps setMinute:59];
[comps setSecond:59];

NSDate *today = [calendar dateFromComponents:comps];

To get tomorrow at 23:59:59:

NSDate *now = [NSDate dateWithTimeIntervalSinceNow:24 * 60 * 60]; // 24h from now
NSCalendar *calendar = [NSCalendar currentCalendar];

NSDateComponents *comps = [calendar components:NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit 
                                      fromDate:date];

[comps setHour:23];
[comps setMinute:59];
[comps setSecond:59];

NSDate *tomorrow = [calendar dateFromComponents:comps];

Answer 2

Let's assume:

static const unsigned long seconds_per_day = 60 * 60 * 24;

You can get now and now+24 hours with:

NSDate* today = [NSDate date]; // set for today
NSDate* tomorrow = [today addTimeInterval:seconds_per_day];

In order to get midnight for the given day, it's important to remember that NSDate* is toll-free bridged to CFDateRef, which provides some additional APIs you'll want to use. In particular, you can convert an NSDate to a CFAbsoluteTime with CFDateGetAbsoluteTime:

CFAbsoluteTime abstime = CFDateGetAbsoluteTime(reinterpret_cast<CFDateRef>(myNSDate));
long long      inttime = static_cast<long long>(abstime);

inttime = (inttime / seconds_per_day) * seconds_per_day; // clips the time to midnight

NSDate* myNSDateAtMidnight = reinterpret_cast<NSDate*>(CFDateCreate(NULL,
                                                       static_cast<CFAbsoluteTime>(inttime)));

... which you can wrap into a function to round both today and tomorrow to midnight.