Model a tree structure in Core Data

Question

I want to implement a multi-way tree using core data. There's a "Plan" entity in my core data model.

            Plan
           /  |  \
        Plan Plan Plan
     /  | \   |     |   \
   Plan Plan ...

The plan of the higher level will have to-many relationship with the sub-plans.

So how should I set the relationship?

Answer 1

I would define

• a to-many relationship subplans (or children) from the Plan entity to itself, with the "Delete Rule" set to "Cascade",
• a to-one relationship superplan (or parent) from the Plan entity to itself, with the "Delete Rule" set to "Nullify",
• and set these as inverse relationships of each other.

If you delete one Plan object, then automatically

• all sub-plans are deleted due to the "Cascade" delete rule, and
• the plan is removed from its parent object due to the "Nullify" delete rule.