Core data fetching entity1 and limiting it from a variable

Question

Sorry if i confuse anyone but i am going to try my best to describe my problem.

I have an entity named Document and another entity named Customer the Document has an attribute named CustomerID and that gets assigned from the Customer attribute CustomerID, and it has a updatedDate attribute.

I want to get the 10 most recent documents but only the most recent per CustomerID.

Answer 1

If i understood you right, you want to get 10 most recent Documents fron a specified customer? That's easy.

NSFetchRequest *request = [[NSFetchRequest alloc] init];
   request.entity = [NSEntityDescription entityForName:@"Document" inManagedObjectContext:managedObjectContext];//Specify the entity Name
   request.predicate = [NSPredicate predicateWithFormat:@"customerID = %@",customerID];//Specify the ID you need
   request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"updatedDate" ascending:YES]];//Sorted by most recent ones
   request.fetchLimit = 10;//You'll get ten latest Documents
   NSError *error = nil;

 latestDocuments =  [managedObjectContext executeFetchRequest:request error:&error];

EDIT

As we found out, that the task is to get ten most recent documents, but just one per customer, i really see no way to do this somehow efficient(i mean,without IN query,that will contain customerID's you've already fetched),but juat to add a new one-to-one elationship to your customer - latestDocument, and a inverse to it, and just make request to the documents,in which isLatestToCustomer is not nil.