Question

I have a single Entity ‘testData’ with three attributes : time , beat , rate. I need to traverse the ‘time’ attribute everytime and store the corresponding values of beat and rate in an NSMutablearray for each.

NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];
NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];


[newManagedObject setValue:[x] forKey:@"timeStamp"];
[newManagedObject setValue:[y] forKey:@"beat"];
[newManagedObject setValue:[z] forKey:@"rate"];



// Save the context.
NSError *error = nil;
if (![context save:&error]) {
     // Replace this implementation with code to handle the error appropriately.
     // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. 
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();

Answer 1

If I am understanding what you are wanting to do:

Do a FetchRequest for that Entity (no predicate) and put the results into an NSArray.

Do a ForIn on the Array you get back and add the objects you need (beat and rate) into their corresponding NSMutableArrays.

Also – you may want to check out MagicalRecord (an open source library that makes dealing with Core Data much more fun 🙂