[iPhone SDK] Truncating NSDates ; Init NSDateComponents from a NSDate

Question

In my application, I have to truncate some of the components of an NSDate, so I can do comparisons.
Basically I am initializing a new NSDate as NOW. So that gives me Minutes, Seconds, Sub-Seconds.
In my current application, I need to ZERO OUT the Seconds, Sub-Seconds.
For the Minutes, I need to evaluate the minutes. If it is after the 30 minute mark, I have to roll it back to 30. If it is between 0 and 29, I have to roll back to 0.
So I need truncate the time to 00 or 30 for the minutes (Day, Hours are not impacted, but the theory is the same if I need to truncate to the week, month, year)
I have been looking and can't find a NSDate truncation method, or other class that will do it for me.
On another forum, they directed me to the NSDateComponents class. Which I probably could use for what I am doing.
The problem I am running into with that class, is initializing it to a specific date (or even NOW directly).
Since on the iPhone I can't use NSCalendar most of the examples of extracting the different components of an NSDate are not available (since they seem to use the NSCalendar functions).
So I can't even brute force initialize the date directly.
The only way I have been able to do is is using a NSDateFormatter which is so overkill, I'll stick with my original method of doing it (which is ~slow~).
So anyone have any other ideas for my above situations?
Or if the Apple guys are reading this: Two things would be very helpfull.
-) A method on the NSDate that would truncate to a specific type (Year, Month, Week, Hour, Minute, Second, with an option to round up/down to a specific integer value)
-) A method on the NSDateComponents to initialize FROM an NSDate, or from NOW

Answer 1

All right, I did some research, and hopefully I've got it right. Here's how it would be done, and I'll tell you what I'm doing line by line:
NSDate *date = [NSDate date];
NSDateComponents *dateComponents = [[NSDateComponents alloc] init];
Creates a new date and new date components. The NSDate is set to now.
dateComponents = [dateComponents components:NSYearCalendarUnit fromDate:date];
This sets the date components to the date components with the date that you specified's current year, I think, but I'm not sure. You can look up NSCalenderUnit and the components:fromDate: method for more information on it.