changing format (for respond_to)

So in my action I have:

- respond_to do |format|
- format.html
- format.iphone
- end

Now I can access action.html and action.iphone, however how would I make
it default to the iPhone view if the user agent is an iPhone. I'm pretty
tired so forgive me for being brief or perhaps missing something
obvious. I tried having the code below as a before_filter, but that
didn't work.

- if request.user_agent =~ /iPhone/
- params[:format] = 'iphone'
- end

Anyway, thanks for your time :slight_smile: