View-based NSOutlineView performs badly

Hi dear community,

I'm currently trying to use a view-based NSOutlineView in my application and everything looks good so far. However, I experience some weird performance issues when using more than one view. I implemented the following method, to provide two views (the default dataCell and headerCell ones, IB creates for a new outline view depening on the kind of item)

- (NSView *)outlineView
 NSOutlineView *)outlineView 
     viewForTableColumn:(NSTableColumn *)tableColumn 
                   item:(id)item {


    NSTableCellView *result = nil;

    if ([item isKindOfClass:[NSMutableDictionary class]]) {
        result = [outlineView makeViewWithIdentifier:@"HeaderCell" owner:self];

        id parentObject = [outlineView parentForItem:item] ? [outlineView parentForItem:item] : groupedRoster;
        [[result textField] setStringValue:[[parentObject allKeys] objectAtIndex:0]];


    } else {
        result = [outlineView makeViewWithIdentifier:@"DataCell" owner:self];

        [item nickname] ? [[result textField] setStringValue:[item nickname]] : [[result textField] setStringValue:[[item jid] bare]];
    }
    return result;
}

When I just call

makeViewWithIdentifier with a single identifier (e.g. just the HeaderCell or just the DataCell)

quite slow and laggy while CPU usage spikes. Could anyone explain why that is?