I want to create an NSButton that sends an action when it is clicked, but when it is pressed for 1 or two seconds it show a NSMenu. Exactly the same as this question here, but since that answer doesn't solve my problem, I decided to ask again.
As an example, go to Finder, open a new window, navigate through some folders and then click the back button: you go to the previous folder. Now click and hold the back button: a menu is displayed. I don't know how to do this with a NSPopUpButton.
Use NSSegmentedControl.
Add a menu by sending setMenu:forSegment: to the control (connecting anything to the menu outlet in IB won't do the trick). Have an action connected to the control (this is important).
Should work exactly as you described.