Bound NSTreeNode - Inserting Children

FROM : Robert Sesek
DATE : Wed Jun 11 21:50:48 2008

Hi all,

I have bound a NSTreeController to a NSOutlineView. I am trying to 
insert child nodes into this structure, but I cannot seem to make it 
work. This is the code I originally used:

- (void)addChildren:(NSArray *)children toNode:(NSTreeNode *)node
{
   NSXMLElement *parent = [node representedObject];
   for (NSXMLNode *child in children)
   {
       [parent addChild:child];
   }
   
   [registerController rearrangeObjects];
}

I figured by updating the NSXML* model and then rearranging it should 
work, but it didn't. So I then wrote code to take advantage of 
NSTreeNode in 10.5:

- (void)addChildren:(NSArray *)children toNode:(NSTreeNode *)node
{
   NSMutableArray *childNodes = [node mutableChildNodes];
   [childNodes removeAllObjects];
   for (NSXMLNode *child in children)
   {
       NSTreeNode *newChild = [[NSTreeNode alloc] 
initWithRepresentedObject:child];
       [childNodes addObject:newChild];
       [newChild release];
   }
}

But this results in this exception: -[NSKeyValueFastMutableArray2 
count]: value for key children of object 0x105a220 is nil:
#0    0x91bdd0d7 in objc_exception_throw
#1    0x94827f2b in +[NSException raise:format:arguments:]
#2    0x94827f6a in +[NSException raise:format:]
#3    0x944b5061 in -[NSKeyValueFastMutableArray2 
_nonNilArrayValueWithSelector:]
#4    0x944b4fa9 in -[NSKeyValueFastMutableArray2 count]
#5    0x9455c5a7 in -[NSKeyValueNotifyingMutableArray addObject:]
#6    0x96f6769f in -[NSTreeControllerTreeNode 
insertObject:inSubNodesAtIndex:]
#7    0x944b50af in -[NSKeyValueFastMutableArray insertObject:atIndex:]
#8    0x944b4f74 in -[NSKeyValueFastMutableArray addObject:]
#9    0x0000446a in -[DebuggerWindowController addChildren:toNode:] at 
DebuggerWindowController.m:278

I've also tried to insert using index paths, but this, too, results 
with the above crash:

- (void)addChildren:(NSArray *)children toNode:(NSTreeNode *)node
{
   [[node mutableChildNodes] removeAllObjects];
   NSIndexPath *ip = [node indexPath];
   for (NSXMLNode *child in children)
   {
       NSTreeNode *newChild = [[NSTreeNode alloc] 
initWithRepresentedObject:child];
       [registerController insertObject:child atArrangedObjectIndexPath:[ip 
indexPathByAddingIndex:0]];
       [newChild release];
   }
}

I have no other ideas for how to get this to work. Basically, the tree 
displayed is incomplete, and as the user expands the tree, data is 
fetched from a server and then inserted beneath a node.

Thanks,
Robert