Question

HI

I am just starting to learn Core Data and one part that confuses me is the inverse relationship. Lets say that I have a entitiy named Photo and one enitity named Photograph, just as in the Stanford course. A photograph has a one to many relationship to photo, and one photo belongs to one photograph.

My question is (I know SQL) is what are the inverse relationships I have to make? This probably has to do with primary/foreign key however I do not understand what inverse relationship does?

Thanks for your time:=)

Answer 1

An inverse relationship maintains data integrity when changes are made to instances of an entity:

You should typically model
relationships in both directions, and
specify the inverse relationships
appropriately. Core Data uses this
information to ensure the consistency
of the object graph if a change is
made (see “Manipulating Relationships
and Object Graph Integrity”). For a
discussion of some of the reasons why
you might want to not model a
relationship in both directions, and
some of the problems that might arise
if you don’t, see “Unidirectional
Relationships.”