Traversing a Relationship Based Upon an Existing Objects

[b.dot]

Hi All,

I have an existing fetchedResultsController representing objects previously fetched for the entity EventLocations. I am trying to figure out how to return a list of unique EventCategories based upon the exiting EventLocations. I can figure out how to do this with one object, but how do I get all of the Events related to the existing selection of objects in EventLocations and then all of the EventCategories related to Events? I realize that there is no join in Core Data. Will I need to iterate through each object? valueForKeyPath?

Can anyone post a link to a specific example or lead me in the right direction? I've been trying to find a more specific example in the documentation, and I seem to end up in areas totally unrelated to this.

Thanks, b.