User Concern example

chargeable.rb

module Chargeable
  extend ActiveSupport::Concern
  
  def charge_order(amount, discount, products)
    create_order(amount, discount, products)
    send_order_charge
    
    # ...
  end
  
  private
  
  def create_order(amount, discount, products)
    # altough we could pass the user as parameter, this concern incorrectly
    # assumes that the user model includes the concern, an implicitness we should avoid

    @order = Order.create!(amount: amount, discount: discount, products: products, user: self)
  end
  
  def send_order_charge
    # logic related to payment process, usually calling an external API
  end
    
  # ...
end