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I have some hierarchical data model that I'd like to present in an NSOutlineView. I'm binding a tree controller to the outline view to provide data and to handle selection and binding to other views.

However, I only want to show only part of the data in my model to the outline view. (Each object in my hierarchy has an array of child objects, but I'd only like some of these child objects to appear as child nodes of the node in the tree.) I wish I could just attach a filter predicate to the tree controller, but it seems that NSOutlineView doesn't support filter predicates.

I think that this design requires an NSOutlineViewDataSource to filter my data model, and an NSTreeController bound to the data source and the outline view. However, none of the binding outlets in the tree controller (Content Array, Content Object, Content Set, etc.) seems appropriate for binding a data source.

Any ideas? Thanks in advance...

David Stein
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2 Answers2

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You can try feeding the data to your array of child objects through an array controller.

Here's how I'd do it. Override the accessor method in your represented object and return a filtered array from your array controller.

Suhas
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In general, NS[Outline|Table]ViewDataSource and Cocoa Bindings is an "either/or" choice. Mixing the approaches, while perhaps not strictly impossible, will likely lead to unpredictable results.

You mention binding a filter predicate to the Outline View itself and not to specific nodes, so I surmise that one filter predicate for all nodes might be "good enough." If that's the case, then one solution to this would be to expose a second children-vending property on your model, maybe filteredChildren, and tell the NSOutlineView to use that to access children instead of the your default/complete children-vending property. If you need functionality like drag reordering, this approach might prove to be non-trivial, but it should be easy to explore this approach regardless.

If you need a different filter for each node, or if the filter changes dynamically, this task would likely have crossed over into being a case that was a good candidate for implementing NSOutlineViewDataSource (and a poor candidate for using Cocoa Bindings.)

ipmcc
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