title: How to using "HeaderCell" of view-based NSOutlineView as group for "DataCell"?
body: <p>I have listed the items in "DataCell" view of NSOutlineView, but I do not know, how to put all of them into custom root group. I mean a default group of NSOutlineView items, but with some subviews (such as buttons or images). And one more, for example I have two groups of items, but one of them has subview, and second there has only a "Hide" toggle button, how can do something like that?</p>
  
  <pre><code>- (NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(id)item {
      if (![item isKindOfClass:[FSEntity class]]) {
          return [outlineView makeViewWithIdentifier:@"HeaderCell" owner:self];
      } else {
          NSTableCellView *cellView = [outlineView makeViewWithIdentifier:@"DataCell" owner:self];
          cellView.textField.stringValue = [((FSEntity *)item) title];
          return cellView;
      }
  }
  </code></pre>
  
  <p>We require the following methods to do that?</p>
  
  <pre><code>- (BOOL)outlineView:(NSOutlineView *)outlineView isItemExpandable:(id)item
  - (BOOL)outlineView:(NSOutlineView *)outlineView isGroupItem:(id)item
  </code></pre>
  
  <p>However, can applications created with these features run on Tiger and Snow Leopard? Or would I have to resort back to cell-based table views? But how to do all of the above with the cell-based NSOutlineView, at least add Square Button into group of items?</p>
  
  <p><strong>NOTE:</strong> I enumerated items based of the protocol of NSURL and so the array does not have a root directory from which they are enumerated.</p>