Are the built-in images in iPhone documented, and is there a list of their names somewhere?

Question

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.

Answer 1

You can get the UITabBarItems and once there search for UIBarButtonItem. Scroll towards the bottom of the screens and you can see all the system images for Tab Bars and Navigation Bars.

Answer 2

I found an up-to-date (iOS7) list of icons for UIBarButtonSystemItem on the official iOS Developer Library, which could be helpful.

UIBarButtonSystemItemDone  
UIBarButtonSystemItemCancel  
UIBarButtonSystemItemEdit  
UIBarButtonSystemItemSave  
UIBarButtonSystemItemAdd  
UIBarButtonSystemItemFlexibleSpace  
UIBarButtonSystemItemFixedSpace  
UIBarButtonSystemItemCompose  
UIBarButtonSystemItemReply  
UIBarButtonSystemItemAction  
UIBarButtonSystemItemOrganize  
UIBarButtonSystemItemBookmarks  
UIBarButtonSystemItemSearch  
UIBarButtonSystemItemRefresh  
UIBarButtonSystemItemStop  
UIBarButtonSystemItemCamera  
UIBarButtonSystemItemTrash  
UIBarButtonSystemItemPlay  
UIBarButtonSystemItemPause  
UIBarButtonSystemItemRewind  
UIBarButtonSystemItemFastForward  
UIBarButtonSystemItemUndo  
UIBarButtonSystemItemRedo  
UIBarButtonSystemItemPageCurl