NSPredicate filtered by year moth day

Question

I use Core Data for storing my data model objects. Each object has NSDate property.

NSDate property has format like below:

2013-03-18 12:50:31 +0000
         


        

Answer 1

While David showed how you can create a predicate, i want to add a easier way to generate a date for 0:00

NSDate *startDate = [NSDate date];
NSTimeInterval lengthDay;

[[NSCalendar currentCalendar] rangeOfUnit:NSDayCalendarUnit 
                                startDate:&startDate
                                 interval:&lengthDay 
                                  forDate:startDate];

startDate now contain a date representing 0:00 for the current time zone of today

NSDate *endDate = [startDate dateByAddingTimeInterval:lengthDay];

Now we can put it into the predicate

NSPredicate *daySpanPredicate = [NSPredicate predicateWithFormat:@"(date >= %@) AND (date < %@)", startDate, endDate];

_{Thanks to MartinR for the improvement.}

Answer 2

If your dates are stored as actual dates then you should use that to your advantage and not fiddle with formats. You can simply create a predicate that checks that if the dates is between two dates (with times). The first date is your date with the time 00:00:00 and the second date is one day after that.

// Create your date (without the time)
NSDateComponents *yourDate = [NSDateComponents new];
yourDate.calendar = [NSCalendar currentCalendar];
yourDate.year  = 2013;
yourDate.month = 3;
yourDate.day   = 18;
NSDate *startDate = [yourDate date];

// Add one day to the previous date. Note that  1 day != 24 h
NSDateComponents *oneDay = [NSDateComponents new];
oneDay.day = 1;
// one day after begin date
NSDate *endDate = [[NSCalendar currentCalendar] dateByAddingComponents:oneDay 
                                                                toDate:startDate
                                                               options:0];

// Predicate for all dates between startDate and endDate
NSPredicate *dateThatAreOnThatDay = 
    [NSPredicate predicateWithFormat:@"(date >= %@) AND (date < %@)", 
                                     startDate, 
                                     endDate]];