_NSArrayControllerTreeNode is often returned by [NSOutlineView itemAtRow:i]. There is no documentation on it. The header for it can be found at http://www.blueboxmoon.com/wiki/?page=Binding%20Tree

As always, be wary of undocumented APIs. Apple will feel no reservations about pulling them right out from under you.

@interface _NSArrayControllerTreeNode : NSObject

// // Get the number of child nodes under this node. //

• (int)count;

// // Get the index path of this node in the tree. //

• (NSIndexPath *)indexPath;

// // Insert the given user object at the specified index number. //

• (void)insertObject:(id)aObject atIndex:(int)nIndex;

// // Insert the given user object at the specified index path, relative // to this node. //

• (void)insertObject:(id)aObject atIndexPath:(NSIndexPath *)indexPath;

// // Returns YES if this node is a leaf (no children), NO if it has children. //

• (BOOL)isLeaf;

// // Get the child node at the given index path, relative to this node. //

• (_NSArrayControllerTreeNode *)nodeAtIndexPath:(NSIndexPath *)indexPath;

// // Get the user object at the given index path, relative to this node. //

• (id)objectAtIndexPath:(NSIndexPath *)indexPath;

// // Retrieve the user object for this node. //

• (id)observedObject;

// // Get the parent node of this node. If this is a top level object the // returned object is of class _NSArrayControllerTreeNode, otherwise it // is of class _NSArrayControllerTreeNode. //

• (id)parentNode;

// // Removes the child node at the given index. //

• (int)removeObjectAtIndex:(int)nIndex;

// // Remove the child node at the given index path, relative to this node. //

• (int)removeObjectAtIndexPath:(NSIndexPath *)indexPath;

// // Set the user object to be observed by this node. Probably a dangerous method // to call when the tree is “active”. //

• (id)setObservedObject:(id)aObject;

// // Change the parent of this node to another node. This moves the called // node to another node in the tree. This method does not appear to fully // work when called directly. It probably is meant to be used in combination // (or via) the insertObject: methods. //

• (id)setParentNode:(_NSArrayControllerTreeNode *)aNode;

// // Set the sort descriptors for this node. This sorts only // the children of this node and not the entire tree. //

• (void)setSortDescriptors:(NSArray *)sortDescriptors;

// // Retrieve the child node at the given index under this node. //

• (_NSArrayControllerTreeNode *)subnodeAtIndex:(int)nIndex;

// // These are completely unknown methods. // //- (void)prune; - Does not delete items. //93b56f88 t -[_NSArrayControllerTreeNode observeValueForKeyPath:ofObject:change:context:] //93b56da4 t -[_NSArrayControllerTreeNode allowsSubnodeAtIndex:] //93b56e80 t -[_NSArrayControllerTreeNode startObservingModelKeyPath:] //93b55dd8 t -[_NSArrayControllerTreeNode updateSubnodes] // nm

@end

Include that header to get rid of warnings when using itemAtRow:

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Do you have examples on how to use this class ? I would like to know how you initialize it with a “user object”. It crashes when I do setObservedObject: on an instance created with alloc-init. Tx.