NSDateFormatter格式化日期的一周

Question

I've been looking for a way to format the following NSDate object:

19 Feb 2013

Like that

18-25 Feb 2013

The 19 occurs within the week between the 18th and the 25th of Feb.

I couldn't an easy method to do so, is there build in functionality in to the NSDateFormater? should I implement it myself?

Answer 1

I don't think there is built in functionality in NSDateFormatter to do this. However, Apple has an example of how to get the NSDate values for the first and last days of a the week given a date. Here's their example on getting the Sunday of the current week:

NSDate *today = [[NSDate alloc] init];
NSCalendar *gregorian = [[NSCalendar alloc]
          initWithCalendarIdentifier:NSGregorianCalendar];

// Get the weekday component of the current date
NSDateComponents *weekdayComponents = [gregorian components:NSWeekdayCalendarUnit
          fromDate:today];

/*
Create a date components to represent the number of days to subtract from the current date.
The weekday value for Sunday in the Gregorian calendar is 1, so subtract 1 from the number of days to subtract from the date in question.  (If today is Sunday, subtract 0 days.)
*/
NSDateComponents *componentsToSubtract = [[NSDateComponents alloc] init];
[componentsToSubtract setDay: 0 - ([weekdayComponents weekday] - 1)];

NSDate *beginningOfWeek = [gregorian dateByAddingComponents:componentsToSubtract
          toDate:today options:0];

/*
Optional step:
beginningOfWeek now has the same hour, minute, and second as the original date (today).
To normalize to midnight, extract the year, month, and day components and create a new date from those components.
*/
NSDateComponents *components =
     [gregorian components:(NSYearCalendarUnit | NSMonthCalendarUnit |
          NSDayCalendarUnit) fromDate: beginningOfWeek];
beginningOfWeek = [gregorian dateFromComponents:components];

Since Sunday is not the beginning of the week in all locales, they also show how to get the beginning of the week as defined by the calendar's locale:

NSDate *today = [[NSDate alloc] init];
NSDate *beginningOfWeek = nil;
BOOL ok = [gregorian rangeOfUnit:NSWeekCalendarUnit startDate:&beginningOfWeek
                     interval:NULL forDate: today];