Core Data add relationship as unique constraint- iOS

Question

I'm developing an application with core data. There are many entities that uses relationships and in many of them they are the primary key.
I'm trying to use the unique constraints feature in the xcdatamodel but there is no way to compile the project.
The error that Xcode shows is:
cdtool cannot compile.

It only happens with relationships, if I add an attribute in the constraints there is no problem.

I would like to know if I'm doing something wrong or the relationship cannot be a unique constraint.

EDIT 1:

Voiced

If possible, try to give picture of data model and relationships – Importance

I have edited with the data model. – Contrasty

still seems to happen in iOS11 :( – Overstate

As far as I know you can't add relationship in constraints. Go to the entity Articulo and add a constraint there. You are adding it from BodegonReg – Skivvy

constraints field must be string type. So it can't be relationship. I know I am very late in replying. But still posting if some still have any confusion about it. – Spinks

Answer 1

`Articulo` is an entity, it's not the property you can set constraints. You should select `Ariculo` and add constraint `ariculoId`(this is the proper of Articulo) to it to make `Ariculo` is unique. In your diagram, `arculo_id` is the relationship. You may not set constraint on it possible.

Think about if the relationship is oneToMany, what you should do?

EDIT:

Tested on Xcode 15, no errors, BUT it doesn't work.

See the image below. bar is the to-one relation:

Here is the result.

Then we try to set Bar's name as the constraint: Still not work!

So far, seems To-One has no uniqeness feature.

Aerometry

Answer 2

This can also happen when in the constraints you put the property of the object and not the object! For example if you put entity.attribute

Restriction