Since NSCalendarDate is going to be deprecated in the future, I've
started playing with NSDateComponents. I have a question regarding a
problem I'm having. I'm getting a wacky date returned at line 15. I'm
expecting it to add -3 to the current date, but I get something *way*
in the future. I'm not trying to invent a time machine. Here is the
code I have:
1 NSCalendar *calendar = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
2 NSDate *now;
3 NSDate *startDate;
4 NSDate *endDate;
5 NSDateComponents *comps = [[NSDateComponents alloc] init];
6 NSDateComponents *components = [[NSDateComponents alloc] init];
7 unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |
NSDayCalendarUnit | NSWeekdayCalendarUnit;
8 int x = 0;
9 now = [NSDate date];
10 comps = [calendar components:unitFlags fromDate:now];
11 x = [comps weekday];
12 NSLog(@"Weekday is: %i", x); // prints "Weekday is: 3" to the console
13 [comps setDay:-x];
14 startDate = [calendar dateByAddingComponents:comps toDate:now
options:0];
15 NSLog(@"startDate is: %@", startDate); // prints "startDate is:
4017-02-01 02:32:04 +1100" to the console
If I change it to the following code, it works as expected:
1 NSCalendar *calendar = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
2 NSDate *now;
3 NSDate *startDate;
4 NSDate *endDate;
5 NSDateComponents *comps = [[NSDateComponents alloc] init];
6 NSDateComponents *components = [[NSDateComponents alloc] init];
7 unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |
NSDayCalendarUnit | NSWeekdayCalendarUnit;
8 int x = 0;
9 now = [NSDate date];
10 components = [calendar components:unitFlags fromDate:now];
11 x = [components weekday];
12 NSLog(@"Weekday is: %i", x); // prints "Weekday is: 3" to the console
13 [comps setDay:-x];
14 startDate = [calendar dateByAddingComponents:comps toDate:now
options:0];
15 NSLog(@"startDate is: %@", startDate); // prints "startDate is:
2008-06-28 02:36:48 +1000" to the console
What I don't understand is why just trying to add -3 in the first lot
of code gives me a strange date. Why do I need to get two different
NSDateComponents to do what I want to do, or am I missing something?
I've read the docs: file:///Developer/Documentation/DocSets/com.apple.ADC_Reference_Library.CoreReference.docset/Contents/Resources/Documents/documentation/Cocoa/Conceptual/DatesAndTimes/Articles/dtCalendars.html
but haven't found an answer.
