Most of the time I don't want to render a layout when the request comes from AJAX. To this end I've been writing render :layout => !request.xhr? frequently in my controller actions.

How can I make this the default? I.e., I'd like to be able to write

def new
  Post.find(params[:id])
end

and have the functionality be

def show
  Post.find(params[:id])
  render :layout => !request.xhr?
end

(I'm fine manually specifying a layout in the rare cases in which I want to use one.)