What are all the steps should be taken while shifting a core data programs location?

Question

Hi friends,

I did a program using core data and saved it in my desktop. The entities, relationships are available in .xcdatamodel file. Then i copied my entire program into some other folder in disk and erased the original file placed in desktop.

Now the copied program did not work. The managed objects are null. What changes must i do while shifting or copying a core data program? I did not add any entities or relationships in my program further.