Core Data and +[NSExpression expressionForFunction:...]
Core Data and +[NSExpression expressionForFunction:...]
- Subject: Core Data and +[NSExpression expressionForFunction:...]
- From: Ron Aldrich <email@hidden>
- Date: Wed, 25 Nov 2009 17:08:51 -0800
Hello All,
I'm trying to query a Core Data database which contains geoLocation information for all of the objects of type "Photo" which are within a specified distance of a target point, using the following code.
- (NSArray*) photosNearLatitude: (NSNumber*) inLatitude
longitude: (NSNumber*) inLongitude
{
NSExpression *theLHS = [NSExpression expressionForFunction: [NSExpression expressionForEvaluatedObject]
selectorName: @"distanceFromLatitude:longitude:"
arguments: [NSArray arrayWithObjects:
[NSExpression expressionForConstantValue: inLatitude],
[NSExpression expressionForConstantValue: inLongitude],
nil]];
NSExpression* theRHS = [NSExpression expressionForConstantValue: [NSNumber numberWithDouble: 0.1]];
NSPredicate* thePredicate = [NSComparisonPredicate predicateWithLeftExpression: theLHS
rightExpression: theRHS
modifier: NSDirectPredicateModifier
type: NSLessThanOrEqualToPredicateOperatorType
options: 0];
NSManagedObjectContext* theManagedObjectContext = [self managedObjectContext];
NSFetchRequest* theFetch = [[[NSFetchRequest alloc] init] autorelease];
theFetch.entity = [NSEntityDescription entityForName: @"Photo"
inManagedObjectContext: theManagedObjectContext];
theFetch.predicate = thePredicate;
NSError* theError = NULL;
NSArray* theResults = [theManagedObjectContext executeFetchRequest: theFetch
error: &theError];
return theResults;
}
The "Photo" class has the following selector.
- (NSNumber*) distanceFromLatitude: (NSNumber*) inLatitude
longitude: (NSNumber*) inLongitude
My problem is that when I call "executeFetchRequest", an exception occurs:
2009-11-25 16:55:20.633 Serendipity[8498:a0f] Unsupported function expression FUNCTION(SELF, "distanceFromLatitude:longitude:" , 47.71283333333334, -122.225)
-[Photo distanceFromLatitude:longitude:] is never called.
Can anyone suggest what might be going wrong?
- Ron Aldrich
_______________________________________________
Cocoa-dev mailing list (email@hidden)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden