coupon_form.html.erb

<%= form_for @coupon do |f| %>
  <% if @coupon_service.stripe_coupon %>
     <%= @coupon_service.stripe_coupon_id %> (<%= @coupon_service.discount %>)
  <% end %>

  <%= f.text_field :stripe_id, placeholder: "#{ @coupon_service.stripe_coupon ? 'Update Promo Code' : 'Promo Code'}", value: "#{@coupon_service.stripe_coupon ? @coupon_service.stripe_coupon_id : nil }", :required => true %>

  <%= f.submit "#{ @coupon_service.stripe_coupon ? 'Update' : 'Save'}", class:'btn btn-info btn-block' %>
<% end %>