example.rb

# somewhere else, maybe in your controller or your checkout service class or something

def process_order
  if @item.stripe_card_token.present?
    status = StripeProcessor.process_new_card(@order, @item.stripe_card_token)
  else
    status = StripeProcessor.process_customer(@order, @item.stripe_customer_token)
  end

  if status == :success
    handle_payment_success
  else
    handle_payment_failure
  end
end

stripe_processor.rb

# Stateless (for now), run either:
#
#   StripeProcessor.process_new_card(order, card_token)
#
#   or
#
#   StripeProcessor.process_customer(order, customer_token)
#
# to process an order.
#
# card_token and customer_token are fields that should come from your
# payment form.
#
# Order must be an instance that responds to:
#   .stripe_customer_id=, .charge_id=, .charge!, .total_price_in_cents,
#   .user.email, .id, .valid?, .stripe_error, .fail!, .failed?
#
# Returns either :success, :invalid, or :failure.
class StripeProcessor
  class << self
    def process_new_card(order, card_token)
      return :invalid unless order.valid?
      customer = create_customer(order, card_token)
      process_with_stripe(order, customer)
    rescue Stripe::CardError => e
      handle_card_error(order, e)
    end

    def process_customer(order, customer_token)
      return :invalid unless order.valid?
      customer = Stripe::Customer.retrieve(customer_token)
      process_with_stripe(order, customer)
    rescue Stripe::CardError => e
      handle_card_error(order, e)
    end

    private

    def process_with_stripe(order, customer)
      charge = create_charge(order, customer)
      order.stripe_customer_id = customer.id
      order.charge_id = charge.id
      order.charge!
      :success
    end

    def create_customer(order, card_token)
      Stripe::Customer.create(
        email: order.user.email,
        card: card_token
      )
    end

    def create_charge(order, customer)
      Stripe::Charge.create(
        customer: customer.id,
        amount: order.total_price_in_cents,
        description: "Tradyo Order ##{order.id}",
        currency: 'cad',
        capture: true
      )
    end

    def handle_card_error(order, e)
      order.stripe_error = e.message
      order.fail! unless order.failed?
      :failure
    end
  end
end