NSTableView Drag and Drop not working

I'm trying to set up very basic drag and drop for my NSTableView. The table view has a single column (with a custom cell). The column is bound to an NSArrayController, and the array controller's content array is bound to an NSArray on my controller object. The data displays fine in the table. I connected the dataSource and delegate outlets of the table view to my controller object, and then implemented these methods:

- (BOOL)tableView:(NSTableView *)aTableView writeRowsWithIndexes:(NSIndexSet *)rowIndexes toPasteboard:(NSPasteboard *)pboard
{
    NSLog(@"dragging");
    return YES;
}

- (NSDragOperation)tableView:(NSTableView*)tv validateDrop:(id <NSDraggingInfo>)info proposedRow:(NSInteger)row proposedDropOperation:(NSTableViewDropOperation)op
{
    return NSDragOperationEvery;
}

- (BOOL)tableView:(NSTableView *)aTableView acceptDrop:(id <NSDraggingInfo>)info
              row:(NSInteger)row dropOperation:(NSTableViewDropOperation)operation
{
    return YES;
}

I also registered the drag types in -awakeFromNib:

#define MyDragType @"MyDragType"

- (void)awakeFromNib
{
    [super awakeFromNib];
    [_myTable registerForDraggedTypes:[NSArray arrayWithObjects:MyDragType, nil]];
}

The problem is that the -tableView:writeRowsWithIndexes:toPasteboard: method is never called. I've looked at a bunch of examples and I can't figure out anything I'm doing wrong. Could the problem be that I'm using a custom cell? Is there something I'm supposed to override in the cell subclass to enable this functionality?

EDIT: Confirmed. Switching the custom cell for a regular NSTextFieldCell made dragging work. Now, how do I make drag and drop work with my custom cell?

I fixed the issue. There seems to be an issue with using bindings with custom NSCells in a table view. Switching to the traditional NSTableViewDataSource methods rather than bindings and an array controller solved it.