IOS basic data on how to prevent duplicate inclusion

Question

I am new to IOS Programmer, and I want to store data from the user interface for the main data, for simplicity we take the Student example, each student has rollNo, which is unique and not null. I just want to confirm that one day a student with a particular roll will not say 101, then the main data will not be stored by a new student with the same roll as with 101.

How to do it?

Also I know very well that the underlying data is not a database, so there is no concept of any primary key, so there is an alternative to this?

I also searched the net and I got some answers from stackoverflow it self, but they all say that they get all the data from the main data using the fetch request and compare the new object with all the objects that are retrieved from the extracted request, but that’s not it what I'm looking for, it degrades performance when there are no more objects in the main data.

Answer 1

Check out Plain Notes, it's built with CoreData, it's cheap and well-commented, you can easily find out how CoreData works: http://goo.gl/N18xzj

This should help you.