You could do this:
int dayOfYearForDate(NSDate *_date)
{
NSCalendar *calendar = [[NSCalendar alloc]
initWithCalendarIndentifier:NSGregorianCalendar]];
int day = [calendar ordinalityOfUnit:NSDayCalendarUnit
inUnit:NSYearCalendarUnit forDate:_date];
return day;
}
I've never benchmarked this, but it's certainly a lot less code.
Eliza
On Aug 18, 2008, at 8:32 AM, Tom Bernard wrote:
My application needs to obtain the day of year for a given date. In
the
past, this was easily done with an NSCalendarDate.
// NSCalendarDate faces deprecation
int dayOfYearForDate1(NSDate *_date)
{
NSTimeZone *gmtTimeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
NSCalendarDate *calendarDate = [_date dateWithCalendarFormat:nil
timeZone:gmtTimeZone];
int day = [calendarDate dayOfYear];
return day;
}
NSCalendarDate faces deprecation: "Use of NSCalendarDate strongly
discouraged. It is not deprecated yet, however it may be in the next
major
OS release after Mac OS X v10.5. For calendrical calculations, you
should
use suitable combinations of NSCalendar, NSDate, and
NSDateComponents, as
described in Calendars in Dates and Times Programming Topics for
Cocoa."
The above advice led to two alternate functions:
int dayOfYearForDate2(NSDate *_date)
{
NSTimeZone *gmtTimeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
NSCalendar *calendar = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
[calendar setTimeZone:gmtTimeZone];
NSDateComponents *components = [calendar
components:NSYearCalendarUnit
fromDate:_date];
int year = [components year];
components = [[NSDateComponents alloc] init];
[components setYear:year -1];
[components setMonth:12];
[components setDay:30];
[components setHour:23];
[components setMinute:59];
[components setSecond:59];
NSDate *lastYear1230 = [calendar dateFromComponents:components];
[components release];
components = [calendar components:NSDayCalendarUnit
fromDate:lastYear1230 toDate:_date options:0];
int day = [components day];
[calendar release];
return day;
}
int dayOfYearForDate3(NSDate *_date)
{
NSTimeZone *gmtTimeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
NSCalendar *calendar = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
[calendar setTimeZone:gmtTimeZone];
NSDateComponents *components = [calendar
components:NSYearCalendarUnit
fromDate:_date];
int year = [components year];
NSString *dateString = [NSString stringWithFormat:@"%d-12-30
23:59:59
-0000", year - 1];
NSDate *lastYear1230 = [NSDate dateWithString:dateString];
components = [calendar components:NSDayCalendarUnit
fromDate:lastYear1230 toDate:_date options:0];
int day = [components day];
[calendar release];
return day;
}
To decide whether to use dayOfYearForDate2() or dayOfYearForDate3()
in my
application, I benchmarked all three functions:
dayOfYearForDate1(): 8.76544 microseconds
dayOfYearForDate2(): 46.9595 microseconds
dayOfYearForDate3(): 74.5191 microseconds
(The above times include 0.4 microseconds attributable to the testing
overhead.)
Since Apple's engineers would not throw away a perfectly good object
without
providing something better, I must be doing things the hard way.
What is the
easy way?
Thanks in advance.
++ Tom
Tom Bernard
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