I discovered somewhat by accident that if you make a UIButton in Interface Builder and type in Plus in the image field, a + image appears for the button. A similar result comes from typing Minus.

I am wondering if this is a bug, or if there is some way the poor programmers can access the built-in general GUI images from other apple apps, such as the green +, the red -, the detail disclosure chevron, the big red "Delete Contact" or similarly styled button, etc.

Has anyone else encountered this, or know where to access these things in Xcode?

It makes sense to me that they should be usable, cause the Apple HIG seems to be all about making things recognizable and intuitive, and using them the way other apps use them.