IoC

gem 'ruby-ioc'

IoC::Container.init do |container|
  # singleton value
  container.register(:checkout_repository, CheckoutRepository)
  
  # new instance value
  container.register(:checkout_service) { CheckoutService.new }
end

class  CheckoutService
  inject :checkout_repository
  
  def  call(checkout)
    # valid checkout
    # ...
    # ...
    checkout_repository.save(checkout)
  end
end