On 4 Nov 2009, at 9:15 PM, Rob Keniger wrote:
I have a Core Data model which consists of a simple tree of a
particular entity, which has two relationships, parent and children.
I have an NSTreeController managing the model, with an NSOutlineView
bound to the NSTreeController.
This works fine if I set the fetch predicate of the NSTreeController
in Interface Builder to "parent == nil".
My problem is that I need a single root object, but this should not
display in the outline view, only its children should be displayed
at the top level of the outline view. My entity has an attribute,
isRootItem, that is true for the root item only.
Here is what I did, for a small tree: My document keeps the root
object as a KVO property -- I do not rely on a fetch.
I declare classes for my tree-element entities. so I could implement a
method, -(NSArray *)orderedChildren, to return the "children" set,
sorted as needed.
I exposed the document (and thus, indirectly, the root) through an
NSObjectController.
I bound the tree controller's content _array_ to that root object's
orderedChildren key. (Document NSObjectController ->
root.orderedChildren). Members of the content array appear as top-
level nodes in the outline.
My tree has constant structure, so I can't make any comment on mutation.
I'm sorry I have trouble making bindings clear from text alone. And,
my experience on this is shallow. I hope at least I've given you
something you can use to explore.
— F
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