respond_to, mime types and excel

Hello All,

I'm trying to figure out how respond_to actually works, especially with the increased focus on REST.

After I set a MIME type for Excel

Mime::Type.register "application/", :xls

In my index action's respond_to block

I have format.xls { @parts = Part.find(:all)         headers['Content-Type'] = "application/"         headers['Content-Disposition'] = "attachment; filename=\"parts-inventory-#{"%m-%d-%Y")}.xls\""         headers['Cache-Control'] = ''         render( :action=>"inbound.rxml", :layout => false) }

but how do i actually trigger the action to return the spreadsheet instead of the HTML page?

when i try index.xls it tries to render the show function.

If anyone can explain this that would be much appreciated.