Comparing certain components of NSDate?

How would I compare only the y开发者_开发知识库ear-month-day components of 2 NSDates?

So here's how you'd do it:

NSCalendar *calendar = [NSCalendar currentCalendar];
NSInteger desiredComponents = (NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit);

NSDate *firstDate = ...; // one date
NSDate *secondDate = ...; // the other date

NSDateComponents *firstComponents = [calendar components:desiredComponents fromDate:firstDate];
NSDateComponents *secondComponents = [calendar components:desiredComponents fromDate:secondDate];

NSDate *truncatedFirst = [calendar dateFromComponents:firstComponents];
NSDate *truncatedSecond = [calendar dateFromComponents:secondComponents];

NSComparisonResult result = [truncatedFirst compare:truncatedSecond];
if (result == NSOrderedAscending) {
  //firstDate is before secondDate
} else if (result == NSOrderedDescending) {
  //firstDate is after secondDate
}  else {
  //firstDate is the same day/month/year as secondDate
}

Basically, we take the two dates, chop off their hours-minutes-seconds bits, and the turn them back into dates. We then compare those dates (which no longer have a time component; only a date component) and see how they compare to eachother.

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Check out this topic NSDate get year/month/day

Once you pull out the day/month/year, you can compare them as integers.

If you don't like that method

Instead, you could try this..

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];

[dateFormatter setDateFormat:@"yyyy"];
int year = [[dateFormatter stringFromDate:[NSDate date]] intValue];

[dateFormatter setDateFormat:@"MM"];
int month = [[dateFormatter stringFromDate:[NSDate date]] intValue];

[dateFormatter setDateFormat:@"dd"];
int day = [[dateFormatter stringFromDate:[NSDate date]] intValue];

• And another way...

  NSDateComponents *dateComp = [calendar components:unitFlags fromDate:date];
  
  NSInteger year = [dateComp year];
  
  NSInteger month = [dateComp month];
  
  NSInteger day = [dateComp day];
  

Since iOS 8 you can use -compareDate:toDate:toUnitGranularity: method of NSCalendar.

Like this:

    NSComparisonResult comparison = [[NSCalendar currentCalendar] compareDate:date1 toDate:date2 toUnitGranularity:NSCalendarUnitDay];

With the the -[NSDate compare:] method - NSDate Compare Reference