Charging customers during registration with Devise

application.rb

module Foo
  class Application < Rails::Application
    # Keep the credit card data out of your logs
    config.filter_parameters += [:password, :credit_card]
  end
end

new.html.haml

= form_for User.new, as: :user, url: user_registration_path do |f|
  - # Regular user details

  = f.fields_for :credit_card do |cc|
    - # Regular CC details

registrations_controller.rb

# CreditCard: wraps CC data from the client. Also works if you're using an encrypted form
#             of the CC data. Not sure if Stripe does this, but Braintree allows it.

# PaymentProcessor: wraps interaction with the payment processor (Stripe, Braintree, etc).
#   #charge: hits the payment API with card data or token

# PaymentProcessor::Charge: wraps the charge from the payment processor
#   #customer_id: generated while adding the customer to the payment processor system
#                 and submitting the card data.

class RegistrationsController < Devise::RegistrationsController
  def create
    credit_card = CreditCard.new(card_params) # Wrap the CC data
    @user = User.new

    if @user.valid?
      payment_processor = PaymentProcessor.new # Wrap payment processor API
      charge = payment_processor.charge(credit_card)

      if charge.success?
        # charge.customer_id is the payment processor
        @user.customer_id = charge.customer_id
        @user.save
      else
        @user.errors[:base] << charge.error_messages
        render :new
      end
    else
      render :new
    end
  end

  def card_params
    @card_params ||= params[:user].delete(:credit_card)
  end
end

routes.rb

Foo::Application.routes.draw do
  devise_for :users, controllers: { registrations: 'registrations' }
end

i think it looks clean !