EmptyPanel sample for mac, How can I set textField programmatically?

I want to set TextField's text programmatically in MAC. But it doesn't work.

In EmptyPanel sample, I called setStringValue function at the end of EmptyPanelPlugin::AddWidgets() function like below.

#ifdef MAC_ENV
...
[calculator->output setStringValue:@"3333"];
#endif

When I click "Third Party Panel" menu, output text doesn't set to "3333".

How can I set this TextFiled programmatically?