Q: NSTextField with automatic NSNumberFormatter in Interface Builder I've been making iOS apps for awhile, but I'm trying my hand at MacOS development. I'm adding an NSTextField to my UI and I noticed in Xcode that one of the options in the graphical widgets is "NSTextField with NSNumberFormatter" which implies to me that I'll be able to restrict the input of the field to numbers and configure the formatter in some way. 
When I add the NSTextField with NSNumberFormatter to my UI, I can see it has a formatter outlet which appears to be kind of linked to an NSNumberFormatter (although the name is a little grayed out). However, I can't figure out any way to interact with or configure that NSNumberFormatter. 
Any help?

A: to configure the number formatter, you can ( after you've selected the formatter ) open the Attributes inspector, select the behavior you want and customize the formatter. At least that worked for me in XCode 4. 
– moritz


A: To access the NSNumberFormatter, you have to select it in the dock (that list of objects on the left side of the XCode 4 Interface Builder [IB] window). 
If the dock isn't in outline view, e.g., it just shows about 4 icons, click the triangle-in-a-square-button at the bottom of the dock. The dock should now show a "Placeholders" section and  an "Objects" section; the objects are your UI objects in a hierarchical outline view.
In the IB window, click your NSTextField; that'll highlight the corresponding Text Field Cell in the outline (you may have to twiddle down some disclosure triangles to see it). The Text Field Cell should have a disclosure triangle; twiddle it down to reveal the Number Formatter. Select it, and you should now be able to manipulate it in the Inspector panel.
(There are a lot of things non-obvious like that in XCode. When in doubt, examine your UI object in the Dock's outline view, or prowl the menus with that object selected. It's amazing--and often useful--what you can discover lurking there!
