edit_update_with_respond_to.rb

def update
  @movie = Movie.find params[:id]
  @movie.update_attributes!(params[:movie])
  respond_to do |client_wants|
    client_wants.html {  redirect_to movie_path(@movie)  } # as before
    client_wants.xml  {  render :xml => @movie.to_xml    }
  end
end