show close button select tab

[Sp1DeRok]

There is the opportunity to show the Close button when displaying select tab?
I tried to add

• (void) tabView: (NSTabView *) aTabView willSelectTabViewItem: (NSTabViewItem *) tabViewItem {
      
       [tabBarControl setAllowsBackgroundTabClosing: NO];
  }

But the program does not work.