Distance group NSFetchedResultsController sections

I'm using Core Data for a tableview. My data is ordered by the distance from your current location. What I'd like is to have a new section for items with 5, 10 and 20 miles.

My distance value is stored in the data store as an NSInteger and I get it out using a NSNumber in my object model.

I've done a bit of searching around and found that I need to use the开发者_StackOverflow sectionNameKeyPath attribute to make the data sectioned.

My problem is that I don't know the best way to group the data. During my searches I came across either a transient property or using a category of NSNumber to work out which section the item should be in.

Are either of these methods the best way of getting my end result, if so, can anyone provide any details on how to implement it?

Thanks.

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You should add a derived attribute to the object (it's not strictly needed in the model), let's name it range. I'd make it a read only property, you can cache the value or not.

When it's 0-5, return 5, 5.x - 10 return 10, etc.

Then set range as your sectionNameKeyPath.

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If you want a highly customized section behavior, you need to subclass NSFetchedResultsController to give you the behavior you want. See the NSFetchedResultsController class docs for details.

You will need to subclass in this case because your not looking at a single ordered attribute like the alphabetized first letter of a string attribute but rather a range in which each attribute falls into.

This is a cleaner solution than altering the data model because you can use it to display the data many different ways in many different tableviews without having to muddy up your data model.