gistfile1.rb

  def show
    # By making it a bang (!) finder it raises RecordNotFound if nothing's found.
    @movie = Movie.find_by_channel_id!(params[:id])

    # We found something, render it as XML
    respond_to do |format|
      format.xml { render :xml => @movie }
    end

  # Oh noes. Nothing found. Tell ze user with a 404.
  rescue ActiveRecord::RecordNotFound
    respond_to do |f|
      # Check what to actually render as XML here. Don't think a string is right.
      f.xml { render :xml => "Not Found", :status => :not_found }
    end
  end