NSDate between two given NSDates

Question

I am interested in creating a method to find if the current date falls between certain times on any given day. It is for a scheduling program, so I want to find what event is occurring at the current time. Every day has the same set of times: 820-900, 900-940, 940-1020, etc. Since this must be done on any given day I do not know how to create an NSDate with a certain time. I think this might be done with NSTimeInterval but I am not sure how to instantiate that.

Answer 1

This isn't perfect, but you could use [NSDate compare:] to check your date against both boundaries:

NSDate *firstDate = ...
NSDate *secondDate = ...

NSDate *myDate = [NSDate date];

switch ([myDate compare:firstDate]) {
    case NSOrderedAscending:
        NSLog(@"myDate is older");
        // do something
        break;
    case NSOrderedSame:
        NSLog(@"myDate is the same as firstDate");
        // do something
        break;
    case NSOrderedDescending:
        NSLog(@"myDate is more recent");
        // do something
        break;
}

switch ([myDate compare:secondDate]) {
    case NSOrderedAscending:
        NSLog(@"myDate is older");
        // do something
        break;
    case NSOrderedSame:
        NSLog(@"myDate is the same as secondDate");
        // do something
        break;
    case NSOrderedDescending:
        NSLog(@"myDate is more recent");
        // do something
        break;
}

Or more briefly:

BOOL between = NO;

if (([myDate compare:firstDate] == NSOrderedDescending) &&
    ([myDate compare:secondDate] == NSOrderedAscending)) {

    between = YES;
}

I'm sure there's a better way to do complex date comparison, but this should work.

Answer 2

Take a look at -[NSCalendar components:fromDate:]. It will let you 'decompose' a date into its various components, and then you can, in this instance, look at the hour and minute.

Answer 3

The easiest way to do this would be to use -timeIntervalSinceReferenceDate to turn each of your dates into an NSTimeInterval typed value, which is really just a double.

NSTimeInterval rightNow = [[NSDate date] timeIntervalSinceReferenceDate];

From there, determining if a date is in between any given two dates is just a matter of simple numeric comparisons.

If you need to convert from a string representation of a date to an NSDate instance to then retrieve a time interval, use NSDateFormatter.

If you need to create a date from known date components, use NSCalendar. (i.e. you know the year is 2010, the month is 4 and the day is 12, you can use NSCalendar's components to generate an NSDate instance via the -dateFromComponents: method.).

As Ben indicated, NSCalendar's component interface can also be used to suss out the hour & minute to determine if it is in a range (which would seemingly be an atypical usage in that most events don't happen every day at the same time... but... sure... there are reasons to do that, too!)