iOS: Date Components Inquiry - iphone

Question

I was wondering how I would edit the dateComps setDay: to go off 3 days before the date set in the picker. I typed in -3, but that doesn't seem to do the trick.
Any help is much appreciated! Here is my code:
- (IBAction)scheduleNotifButton:(id)sender {
NSCalendar *calendar = [NSCalendar autoupdatingCurrentCalendar];
NSDate *pickerDate = [self.datePicker date];
NSDateComponents *dateComponents = [calendar components:( NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit )
fromDate:pickerDate];
NSDateComponents *timeComponents = [calendar components:( NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit )
fromDate:pickerDate];
NSDateComponents *dateComps = [[NSDateComponents alloc] init];
[dateComps setDay:[dateComponents day]];
[dateComps setMonth:[dateComponents month]];
[dateComps setYear:[dateComponents year]];
[dateComps setHour:13];
[dateComps setMinute:30];
[dateComps setSecond:[timeComponents second]];
NSDate *itemDate = [calendar dateFromComponents:dateComps];
UILocalNotification *localNotif = [[UILocalNotification alloc] init];
if (localNotif == nil)
return;
localNotif.fireDate = itemDate;
localNotif.timeZone = [NSTimeZone defaultTimeZone];
localNotif.alertBody = #"Event is in 3 days!";
localNotif.alertAction = nil;
localNotif.soundName = UILocalNotificationDefaultSoundName;
localNotif.applicationIconBadgeNumber = 0;
[[UIApplication sharedApplication] scheduleLocalNotification:localNotif];
}

Answer 1

When you say you have typed -3, do you mean you used this line?
[dateComps setDay:[dateComponents day] - 3];
This should in fact work.
Also, you can tell the system to fire any next year by just settings the current year to the date components. You can find the current year just the way you found the date components for pickerDate.
After that, you can set the repeatInterval of the local notification to NSYearCalendarUnit, that way it will fire each year.

Answer 2

Here is a code to subtract 3 days from Today(NOW). You can adapt it for your needs:
NSDate *today = [NSDate date];
NSLog(#"NOW:%#",today);
NSCalendar *gregorian = [[NSCalendar alloc]initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *todayComps = [gregorian components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit |NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit fromDate:today];
todayComps.day -=3;
NSDate *dateMinus3Days = [gregorian dateFromComponents:todayComps];
NSLog(#"3 days before NOW:%#",dateMinus3Days);
Your making it too complicated. DateComponents can be modified and then set to a new date.

Answer 3

I think all you need to do is subtract 3 days from the date returned by the date picker, no?
NSDate *pickerDate = [self.datePicker date]
pickerDate = [ pickerDate dateByAddingTimeInterval:-3 * 24 * 60 * 60 ] ; // add this line
Version using date components:
- (IBAction)scheduleNotifButton:(id)sender {
NSCalendar *calendar = [NSCalendar autoupdatingCurrentCalendar];
NSDate *pickerDate = [self.datePicker date];
{
NSDateComponent * deltaComponents = [ [ NSDateComponents alloc ] init ];
deltaComponents.days = -3 ;
pickerDate = [ pickerDate dateByAddingComponents:deltaComponents ] ;
}
NSDateComponents *dateComponents = [calendar components:( NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit ) fromDate:pickerDate];
[dateComps setHour:13];
[dateComps setMinute:30];
NSDate *itemDate = [calendar dateFromComponents:dateComps];
UILocalNotification *localNotif = [[UILocalNotification alloc] init];
if (localNotif == nil)
return;
localNotif.fireDate = itemDate;
localNotif.timeZone = [NSTimeZone defaultTimeZone];
localNotif.alertBody = #"Event is in 3 days!";
localNotif.alertAction = nil;
localNotif.soundName = UILocalNotificationDefaultSoundName;
localNotif.applicationIconBadgeNumber = 0;
[[UIApplication sharedApplication] scheduleLocalNotification:localNotif];
}

Answer 4

Use dateByAddingComponents:toDate:options:
// ...
NSDateComponents *offset = [NSDateComponents new];
[offset setDay:(-3)];
NSDate *date3DaysBefore = [calendar dateByAddingComponents:offset toDate:pickerDate options:0];
// ...