Question

I have got some dates for some events and their ascending order from the database .

Now , I want want some buttons ..

in this structure …

–######## Last Week #####—-
–######## yesterday #####—-

–######## today #####—-

–######## tomorrow #####—-
–######## Next Week #####—-

Now when I press the respected buttons ..
the events in that respected duration should be shown up ..

I mean all the data should be compared with today and all the data should be shorted by this order..

can anyone give me a idea or logic for this ?

Answer 1

The best way to deal with dates is by using NSDateComponents.
for example, to get the date for tomorrow use:

NSCalendar *cal = [NSCalendar currentCalendar];
NSDateComponents *comp = [[[NSDateComponents alloc] init] autorelease];
[comp setDay:1];
NSDate *today = [NSDate date];
NSDate *tomorrow = [cal dateByAddingComponents:comp toDate:today options:0];

So, what you need to do is:

1. Get the dates for all the relevant date categories

2. When you push a button, build a predicate to retrieve only the objects between the two dates. For example, getting all the objects in the “tomorrow” category:

   NSPredicate *pred = [NSPredicate predicateWithFormat:@"date > %@ AND date < %@", tomorrow, nextWeek];
   

You can use a small convenient method for getting the dates, by adding a category to NSDate with this method:

@implementation NSDate (Components)

-(NSDate *) dateByAddingCalendarUnit:(NSCalendarUnit)calendarUnit andCount:(NSInteger) count
{
    NSDateComponents *comp = [[NSDateComponents alloc] init];
    switch (calendarUnit) {
        case NSSecondCalendarUnit:
            [comp setSecond:count];
            break; 
        case NSMinuteCalendarUnit:
            [comp setMinute:count];
            break; 
        case NSHourCalendarUnit:
            [comp setHour:count];
            break; 
        case NSDayCalendarUnit:
            [comp setDay:count];
            break;  
        case NSWeekCalendarUnit:
            [comp setWeek:count];
            break; 
        case NSWeekdayCalendarUnit:
            [comp setWeekday:count];
            break;
        case NSWeekdayOrdinalCalendarUnit:
            [comp setWeekdayOrdinal:count];
            break; 
        case NSMonthCalendarUnit:
            [comp setMonth:count];
            break; 
        case NSYearCalendarUnit:
            [comp setYear:count];
            break; 
        case NSEraCalendarUnit:
            [comp setEra:count];
            break; 
        default:
            break;
    }

    NSCalendar *cal = [NSCalendar currentCalendar];
    NSDate *newDate = [cal dateByAddingComponents:comp toDate:self options:0];
    [comp release];
    return newDate;
}

@end

And use this method like this:

NSDate *lastWeek = [[NSDate date] dateByAddingCalendarUnit:NSWeekCalendarUnit andCount:-1];