Sets the string displayed in the receiver when the user isn’t pressing the mouse button.
- macOS 10.0+
The string to display.
For pull-down menus that get their titles from a menu item, this method simply sets the pop-up button cell’s menu item to the first item in the menu. For pop-up menus, if a menu item whose title matches
a exists, this method makes that menu item the current selection; otherwise, it creates a new menu item with the title
a, adds it to the pop-up menu, and selects it.