Core Data - Unique Values Within a Scope

Question

Hi all,

I am new to Core Data and am trying to figure out how to set up a validation. I am tracking apartment buildings, where each Building entity has one or more Apartment entities. Each Apartment has a unitNumber property, which is unique within the scope of a Building.

There could be multiple Unit records with an identical value for the unitNumber property (i.e., "100A"), but there can not be multiple Unit records with that same unitNumber within the same Building.

So, the question is: how can I validate the uniqueness of an Apartment's unitNumber property within the scope of a Building?

Thanks, Bjorn

Answer 1

I would add a class method on my Apartment custom class which searches for an apartment using the predicate format

@"unitNumber==%d && building==%@",unitNumber,buildingInstance

If the result is nil, create a new apartment, or return the existing one.