ipn.rb

  def create_button(id)
    button = {
      :name => 'test',
      :type => 'buy_now',
      :price_string => '1.23',
      :price_currency_iso => "USD",
      :custom => 'Order123',
      :callback_url => 'http://www.example.com/my_custom_button_callback',
      :description => 'sample description',
      :style => 'custom_large',
      :include_email => true
    }
    "https://coinbase.com/api/v1/buttons" + button.to_query
  end