Thanks Kyle, I'll try to apply that. In the meantime, I also found the
AbstractView sample code which does something similar. I'll see which one fits
my code better.
- Koen.
On Oct 29, 2011, at 5:34 PM, Kyle Sluder wrote:
> 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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