Core Data and NSPredicate: Relationships

2
votes

I have a basic entity that looks like the following:

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The entity is the basic entity in a whole tree. Every GPNode has a parent GPNode and a set of children (GPNode). Theoretically the hierarchy could be endless.

I want to do a query using NSPredicate that delivers me all children and children of children etc. of a specific GPNode. Since the number of steps in the hierarchy aren't defined, I can't work with subqueries in the predicate. Any ideas how to achieve my goal? Thanks in advance.

1
xcodecocoa-touchcore-datanspredicatensmanagedobject
Is there a reason you want to do it with a query instead of just recursively iterating through the children property? - Joachim Kurz

1 Answers

2
votes

You should not use a predicate for this. If required use a predicate to find the parent node that you're interested in. Once you have the parent you should use the relationships defined on the node to navigate the hierarchy. If you need to get an array of all the children you should write a recursive algorithm to traverse the hierarchy and build the list.