To start off, you should read Dates and Times Programming Topics for Cocoa. That will give you a good understanding of using the various date/time/calendar objects that are provided in Cocoa for high-level conversions of dates.
This code snip, however, will answer your specific problem:
- (NSInteger)currentHour
{
// In practice, these calls can be combined
NSDate *now = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:NSHourCalendarUnit fromDate:now];
return [components hour];
}
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