Many-to-many relationship constrains in Core Data

Question

I have entities Word and Tag. Both have To-Many relationship to each other, as well as inverse. The way I need to constrain it that:

• if I delete a Word then only the related Tags which has no Word pointing to them will be deleted
• if I delete a Tag which has Words pointing to it then just nullify those set items.

Is it possible to model?

Answer 1

This is something that needs to be handled in code. You need to create custom subclasses for your Word and Tag entities and implement the -prepareForDeletion method in each. Then you can check the logic and handle it appropriately. I would also set the delete rule for the relationships between the entities as deny