On Sat, Oct 29, 2011 at 1:18 PM, Koen van der Drift
<koenvanderdr...@gmail.com> wrote:
> I'm setting up drag and drop for my NSOutlineView and I want to prevent
> parents being dropped on one of their children. The parent and children are
> all of the Group entity. I understand I need to do this in the
> outlineView:validatedrop method. I think I need to create an NSFetchRequest
> with the NSPredictate to get all the children of the parent, but I don't know
> what the predicate should be.
If your outline view is set up such that children are descendant items
of their parents, you don't even need to round-trip to the model
layer. You could implement something like the following:
// Warning: typed in Mail, not guaranteed to work
- (NSDragOperation)outlineView:(NSOutlineView *)outlineView
validateDrop:(id < NSDraggingInfo >)info proposedItem:(id)item
proposedChildIndex:(NSInteger)index
{
NSArray *draggingItems = ItemsFromDragInfo(info);
NSMutableSet *parentTree = [[NSMutableSet alloc] init];
id parentItem = item;
while (parentItem) {
[parentTree addObject:item];
parentItem = [outlineView parentForItem:item];
}
NSDragOperation op = NSDragOperationMove;
for (id item in draggingItems) {
if ([parentTree containsobject:item]) {
op = NSDragOperationNone;
break;
}
}
[parentTree release];
return op;
}
--Kyle Sluder
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