Question

I’m new at using CoreData and I’m trying to understand how to perform a query on a table. I can use a fetch request to pull all of the records from a table, but I’m looking for a subset. Is there an easy way to do this?

Thanks,
Howie

Answer 1

You have to do something like:

// Init your fetchRequest
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];

NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"entityName" inManagedObjectContext:yourManagedObjectContext];

// create the relation between request and the created entity
[fetchRequest setEntity:entityDescription]; 

// Set your predicate for this request
// For more info take a look at NSPredicate Class Reference
// http://developer.apple.com/mac/library/DOCUMENTATION/Cocoa/Reference/Foundation/Classes/NSPredicate_Class/Reference/NSPredicate.html
[fetchRequest setPredicate:somePredicate];

// Pushing the results into a mutable array
NSMutableArray *mutableFetchResults = [[yourManagedObjectContext executeFetchRequest:fetchRequest error:&error] mutableCopy];

[fetchRequest release];