How to select a style based on the controller?

I know I’ve seen this somewhere before, but my friend Google and I just
can’t seem to recall where.

I would like to change the style of a link (in my application layout)
upon which controller is currently active.

This is what I have, which doesn’t work:

<%= link_to “Part”, part_path, :class => == “parts” ?
‘selectedmenu’ : ‘unselectedmenu’ %>

I’m sure I’ve seen this sort of construct in the past, but I can’t
how to construct it. Specifically, this bombs because name is
undefined. I
can probably figure that one out myself. More generally, is there a
helper method defined to select a specific class based on the