testing Apple Pay on the web with Stripe (Rails)

Following this guide to render an Apply Pay button with Stripe.

Stripe provided a fantastic tutorial to integrate Apple Pay with Stripe. It took me half a day to render a button on the page. Here are the fine details of the guide I overlooked to eventually succeed in rendering Apple Pay.

1) Ensure a credit card exists in your Chrome browser wallet. I had Google Pay in my wallet. It was oddly frustrating, and understandable, Apple Pay didn't recognize Google Pay. Anyways, use a CC

2) Enable HTTPS with ngrok. I'm on ngrok version 2.2.4. Adjust your domain port accordingly

> ngrok http -host-header=rewrite localhost:3000

3) Render text from the controller, explicitly

# In `config/routes.rb` point the weirdly dotted namespaced controller endpoint to `ApplePayController` 
get ".well-known/apple-developer-merchantid-domain-association" => "apple_pay#show"

# `app/controllers/apple_pay_controller.rb` render text
class ApplePayController < ApplicationController
  def show
    respond_to do |format|
      format.html do
        render text: DomainAssociationFile.()
      end
    end
  end
end

I initially served html from the controller. I saw text rendered in the web browser.

When registering my domain with Apple, I got 500 errors.

Apple pinged my controller to retrieve the domain association file. It didn't know how to respond to the HTML I gave back. Stripe expected a text format in the return response. Format it like the above.

# I threw this in a presenter
class DomainAssociationFile
  def self.call
    <<-FILE
      # download and paste your domain association file, here
    FILE
  end
end