Core-Data: Predicate for To-Many Relationships

Question

I have a CoreData model with 4 entities.

Model screenshot -> http://img96.imageshack.us/img96/7857/screenshot20100209at182.png

State

-StateName

Location:

-locationName (attribute)

-locationDescription

-locationActivities (relatinship)

-state (relationship)

LocationActivities:

-location (relationship)

-activity (relationship)

Activities

-activityName(attribute)

-locationsActivities (relationship)

How can i write a query that selects all Locations that have

(activity = 'Golf' OR activity = 'Swimming') AND state = 'LA'

Answer 1

// With some NSManagedObjectContext *moc
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:[NSEntityDescription entityForName:@"Location"
                               inManagedObjectContext:moc]];
[request setPredicate:[NSPredicate predicateWithFormat:
                       @"(locationActivities.activity.activityName == %@ OR 
                          locationActivities.activity.activityName == %@) AND 
                         state.stateName == %@",
                       @"Golf", @"Swimming", @"LA"]];
NSError *error;
NSArray *results = [moc executeFetchRequest:request error:&error];

Basically, do a Core Data fetch as normal, then build the appropriate predicate to filter the results (as described in the Predicate Programming Guide).