How to get the day of week from a given number - objective-c

Question

I want to have the day of week name for a given number, here is the pseudo-code :
getDayStringForInt:0 = sunday
getDayStringForInt:1 = monday
getDayStringForInt:2 = tuesday
getDayStringForInt:3 = wenesday
getDayStringForInt:4 = thursday
getDayStringForInt:5 = friday
getDayStringForInt:6 = saturday
I have tried with the follow code, but some thing is not working ...
- (void) setPeriodicityDayOfWeek:(NSNumber *)dayOfWeek{
gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
dateFormatter = [[NSDateFormatter alloc] init];
NSLocale *frLocale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US"];
[dateFormatter setLocale:frLocale];
[gregorian setLocale:frLocale];
NSDate *today = [NSDate date];
NSDateComponents *nowComponents = [gregorian components:NSYearCalendarUnit | NSWeekCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit fromDate:today];
[nowComponents setWeekday:dayOfWeek];
NSDate *alertDate = [gregorian dateFromComponents:nowComponents];
[dateFormatter setDateFormat:#"EEEE"];
NSLog(#"Day Of Week : %# - Periodicity : %#", dayOfWeek, [dateFormatter stringFromDate:alertDate]);
alert.periodicity = [dateFormatter stringFromDate:alertDate];
}
My log is very strange :
Day Of Week : 0 - Periodicity : monday
Day Of Week : 1 - Periodicity : wenesday
Day Of Week : 2 - Periodicity : friday
Day Of Week : 3 - Periodicity : friday
Day Of Week : 4 - Periodicity : tuesday
Day Of Week : 5 - Periodicity : sunday
Day Of Week : 6 - Periodicity : sunday
Any idea ? any better solution ...

Answer 1

Since this has become the accepted answer, I'll post the "right" solution here too. Credits to Rob's answer.
The whole thing can simply be achieved using the [shortWeekdaySymbols][1] method of NSDateFormatter, so the full solution boils down to
- (NSString *)stringFromWeekday:(NSInteger)weekday {
NSDateFormatter * dateFormatter = [NSDateFormatter new];
dateFormatter.locale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US"];
return dateFormatter.shortWeekdaySymbols[weekday];
}
Original answer
Beware, you're passing a pointer to NSNumber to a method that requires a NSInteger.
The compiler is not warning you since a pointer is indeed an integer, just not the one you would expect.
Consider this simple test:
- (void)foo:(NSInteger)a {
NSLog(#"%i", a);
}
- (void)yourMethod {
[self foo:#1]; // #1 is the boxed expression for [NSNumber numberWithInt:1]
}
This prints something like 185035664, which is the pointer value, i.e. NSNumber * when cast to NSInteger.
You should either use [dayOfWeek integerValue] or directly turn dayOfWeek into a NSInteger in your method signature.
Also I think you're getting something else wrong: from the doc of setWeekday:
Sets the number of weekday units for the receiver. Weekday units are
the numbers 1 through n, where n is the number of days in the week.
For example, in the Gregorian calendar, n is 7 and Sunday is
represented by 1.
Sunday is 1, so you'd better check the correspondence with your representation too.

Answer 2

See https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSDateFormatter_Class/Reference/Reference.html#//apple_ref/occ/instm/NSDateFormatter/weekdaySymbols
Simply use weekdaySymbols to retrieve the dayname.

Answer 3

Thanx to Every one, here is a clean response :
/**
* getting the day of week string for a given day of week number
*
* #param dayOfWeekNumber 0 return sunday, 6 return saturday
*
* #return a string corresponding at the given day of week.
*/
- (NSString*) getDayOfWeekStringForDayOfWeek:(NSInteger)dayOfWeek{
return [[dateFormatter shortWeekdaySymbols] objectAtIndex:dayOfWeek];
}