How to read an object from managedObjectContext in Core Data ( Xcode )

Question

I have a program that gets some numbers in a tableView . I have a Core Data based program that has an entity with some attributes and could bind the columns of the tableview to those attributes. Now I want to have the sum of each column , but couldn't find how I can read each data in rows to add them. I used

NSString* S= [self.managedObjectContext valueAtIndex:1 inPropertyWithKey:@"aColumnName" ];

but I receive this error:

this class is not key value coding-compliant for the key name.

Can anyone help me on that?

Answer 1

Sorry I found it . I should have used @"selection.aColumnName"