NSOutlineViewDraggingRows

How do I implement dragging in an NSOutlineView? More specifically, if I know what rows (and/or parents) are selected how do I drop them without screwing up the indexes?

I’m using something like this right now to:

see what rows are highlighted
see if the parent is highlighted (thus making all the children highlighted as well)
if the child is alone (parent not highlighted), make it a parent
else put the parent in the array and the children should follow (I think)
store the new parents and children in _draggedObjects
and remember the old indexes with _oldRows

(btw, this is only for a one level hierarchy at the moment though feel free to explain in full)

(BOOL)outlineView:(NSOutlineView *)oView writeRows:(NSArray *)rows toPasteboard:(NSPasteboard *)pboard { [self setDragNodeArrayWithRows:rows];

[pboard declareTypes: [NSArray arrayWithObjects: QuestionDragType, nil] owner: self];

_oldRows = rows; }

(void)dragNodeArrayWithRows:(NSArray *)rows { int i;

Node *node; Node *parent;

for (i = [rows count]; i > 0; i–) {

  node = [outlineView itemAtRow:rows objectAtIndex: i] intValue;
    
  if (parent = [node parent]) { // check to see if we're dealing with a root
        
      if ([outlineView isRowSelected:[outlineView rowForItem: parent]]) { // check to see if the parent is highlighted
          [_draggedObjects addObject: parent]; // if so, just add the parent
           
      }
  } else {
      [node setParent:nil]; // make it a parent
      [_draggedObjects addObject: node]; // else, if the child is alone, just add it
  }   } }

I guess this is more of a combination question rather… just: Is what I’m doing now correct, and how can I manage the method:

(BOOL)outlineView:(NSOutlineView *)oView acceptDrop:(id )info row:(int)row dropOperation:(NSTableViewDropOperation)op
JohnDevor

Given:

NSArray* draggedItems = …; NSArray* insertionArray = …; // destination array int insertAtIndex = …; // where the user dropped the items

All we need to do is to adjust insertAtIndex to correspond to the index after removing the draggedItems – that is, every item in draggedItems which is also before insertAtIndex, should move insertAtIndex one back.

This can be expressed like this:

NSMutableSet* dragSet = [NSMutableSet setWithArray:draggedItems]; NSArray* before = [insertionArray subarrayWithRange:NSMakeRange(0, insertAtIndex)]; [dragSet intersectSet:[NSSet setWithArray:before]]; insertAtIndex -= [dragSet count];

Alternatively one could use node-coloring (tagging), similar to what is discussed in NSOutlineViewRemoveItem.

Alright, I’ll try it later. Thanks.

Anyone using this page to get started on implementing this should look out - the above code contains an incorrectly named method. It should be:

(BOOL)outlineView:(NSOutlineView *) oView writeItems:(NSArray *) rows toPasteboard:(NSPasteboard *) pboard

I fell foul of this since the Xcode documentation at first appears to lack these delegate methods and so I cut and pasted the code above as a starting point. The Apple sample code is however correct. The info is in the Xcode docs - just not listed under the delegate methods for NSOutlineView - instead they can be found at NSOutlineViewDataSource protocol –GrahamCox

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