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CoreData and NSCalendarDate/NSDate attributes

Hi,

today I got a bit confused about date attributes in CoreData:
On one hand, the documentation of NSAttributeDescription states that the attribute values are NSDate objects. On the other hand using "Copy method implementations to clipboard" in XCode 2.1 on a date attribute creates the following accessor methods which expect NSCalendarDate objects:

- (NSCalendarDate *)testDate
{
    NSCalendarDate * tmpValue;
    [self willAccessValueForKey: @"testDate"];
    tmpValue = [self primitiveValueForKey: @"testDate"];
    [self didAccessValueForKey: @"testDate"];
    return tmpValue;
}

- (void)setTestDate:(NSCalendarDate *)value
{
    [self willChangeValueForKey: @"testDate"];
    [self setPrimitiveValue: value forKey: @"testDate"];
    [self didChangeValueForKey: @"testDate"];
}

Actually, when fetching an object from an SQLite store, all date attributes contain NSDate objects event if they were once inserted using NSCalendarDate objects.
In my app I currently need NSCalendarDate objects for my date attributes because I have a load of calculation categories for this class.

I tried [NSAttributeDescription _setAttributeValueClassName:@"NSCalendarDate"] on my date attributes at model load time which led to funny exceptions.
The only solution I have found so far is to convert all fetched NSDates into NSCalendarDates in the awakeFromFetch method:

- (void)awakeFromFetch
{
[super awakeFromFetch];
NSDictionary *attributes = [[self entity] attributesByName];
NSEnumerator *attributesEnumerator = [attributes keyEnumerator];
id key;
while (key = [attributesEnumerator nextObject])
{
NSAttributeDescription *attribute = [attributes objectForKey:key];
if(![attribute isTransient] && [attribute attributeType] ==NSDateAttributeType)
{
NSString *name = [attribute name];
id value = [self primitiveValueForKey:name];
if(value)
[self setPrimitiveValue:[NSCalendarDate dateWithTimeIntervalSinceReferenceDate:[value timeIntervalSinceReferenceDate]] forKey:name];
}
}
}

But this has the downside of slowing down the fetch process. (Yes, I know this code can be optimized :-) )

So does anybody know a better way to make CoreData instantiate NSCalendarDate objects at fetch time?

Cheers


 Frank

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