Why is an NSDate in a Core Data managed Object converted to NSTimeInterval?

Question

I have an object with a property with a Date type defined in my xcdatamodeld object. Why has it generated the NSManagedObject class with a NSTimeInterval? And how do I set a

Answer 1

Edit: apparently the dateWithTimeIntervalSince1970 is for NSDateFormatter only. NSDate uses a different reference than NSDateFormatter, which as explained in the comments is in 2001. Sorry for my ignorance.

If you have "Use scalar properties for primitive data types" selected when you generated the NSManagedObject subclasses for your entities, it will use scalar properties like int and float instead of NSNumber. This includes NSDate; It will turn NSDate into an NSTimeInterval which is just a double. This NSTimeInterval is a time interval since the 1970 standard epoch used by Apple (if it's before 1970 it probably is negative).

It's pretty simple to convert the NSTimeInterval back into an NSDate if you need it to, but if you don't have a huge database, then you might not want to bother selecting that checkbox.

To convert this time interval into an NSDate just use [NSDate dateWithTimeIntervalSince1970: timeInterval]; where timeInterval is what you get from the database. This can be put in your NSManagedObject subclass so that when you get that property, you get an NSDate anyway.