Question

I currently have Core Data successfully returning all of the results for a specific entity titled Event:

NSManagedObjectContext *context = [delegate managedObjectContext];
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Event" 
                                                     inManagedObjectContext:context];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDescription];

NSError *error;
NSArray *fetchResults = [context executeFetchRequest:request error:&error];

One property of the Event entity is a string titled tid. I also have an array filterArray that contains all allowed tid values.

How can I get my Core Data request to only return events that have a tid property that matches one of the values in filterArray? I believe the answer relates to NSPredicate but I am not familiar enough with it yet to get it to bend to my will.

Answer 1

Try this:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"tid IN %@", filterArray];

[request setPredicate:predicate];

Have a look at the Aggregate Operations in the Predicate Programming Guide.

EDIT

Have a look at NSPredicate iPhone 3.2 SDK Core Data “IN clause” NSInvalidArgumentException exception. It’s same error you have. The problem was a typo in the column/attribute name. The syntax should be alright, it can’t just find tid.