如何在目标c中获得该月的第n个星期日日期？

Question

How to get first sunday or nth sunday or monday (any day) date in Objective C coding.

For example :- I just want to show date of friendship day in my app every year.

But, friendship comes 1st Sunday of Aug. So, date will change every year. here I need to find what is the date of 1st Sunday in Aug every year.

is there any logic to find the date of nth Sunday.

Answer 1

You need to create a NSDateComponents object and set the appropriate values, In You example you would do:

NSDateComponents *dateComponents = [[NSDateComponents alloc] init];

dateComponents.year = 2011; // set the current year or whatever year you want here
dateComponents.month = 8;
dateComponents.weekday = 1; // sunday is 1, monday is 2, ...
dateComponents.weekdayOrdinal = 1; // this means, the first of whatever weekday you specified

To convert this into a NSDate-object, you just do:

//you may want to use another calendar object here
NSDate *myDate = [[NSCalendar currentCalendar] dateFromComponents:dateComponents];
[dateComponents release]; //don't forget memory management ;)

Answer 2

You want to use NSDateComponents in combination with NSCalendar 's dateFromComponents: method:

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];

NSDateComponents *c = [[NSDateComponents alloc] init];
[c setYear:2012];
[c setWeekday:1]; // Sunday
[c setWeekdayOrdinal:3]; // The 3rd Sunday

for (int i = 1; i <= 12; i++) {
    [c setMonth:i];
    NSDate *date = [gregorian dateFromComponents:c];
    NSLog(@"Date[%i]: %@",i,date);
}

[c release];
[gregorian release];

Answer 3

Here's an example. You can find more information in the Date and Time Programming Guide .

To find the first Sunday in August:

NSDateComponents *components = [[NSDateComponents alloc] init];
[components setWeekday:1]; // Sunday
[components setWeekdayOrdinal:1]; // The first Sunday in the month
[components setMonth:8]; // August
[components setYear:2011];
NSCalendar *gregorian = [[NSCalendar alloc]
                         initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *date = [gregorian dateFromComponents:components];

Answer 4

you check the first day of the month.

unsigned units = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [gregorian components:units fromDate:date];

Get the day using [components day]; <-1 for Sunday.After this it's simple.

Answer 5

You'll want to review the NSCalendar class here.

Of specific interest will be the method - (NSUInteger)ordinalityOfUnit:(NSCalendarUnit)smaller inUnit:(NSCalendarUnit)larger forDate:(NSDate *)date