I want to offer the user the choice of one of n choices. The natural choice is to use a dropdown list box:
Here, "Album name", "Artist name" and "Track name" should be mutually exclusive; only one dropdown may have each distinct value selected.
Each row is also optional - only "Album name", say, may be set. There is currently a separate affordance to add a new case rule.
In the screenie above, you can see the alternative choices are disabled. Is this the best way to handle this? Should the other options be removed from the list instead?
Alternatively, is it best to allow the selection, but display a warning and disallow the "saving" or "confirmation" of these settings with an error message?