fourthmeal#transactions_controller refactor process Blog post about it: http://www.simontaranto.com/2013/12/11/it-all-comes-together-ruby-js-and-functional-programming.html

gistfile1.txt

Before:
def create
    @transaction = current_order.build_transaction(transaction_params)
    @transaction.update(:order_id => current_order.id)
    if @transaction.save
      @transaction.pay!
      if current_user
        current_order.update(:user_id => current_user.id, :status => "paid")
      else
        current_order.update(:status => "paid")
      end
      session[:current_order] = nil
      OrderMailer.order_confirmation(@transaction).deliver
      flash[:notice] = "Successfully created your order!"
      redirect_to transaction_path(@transaction)
    else
      flash[:notice] = "There was a problem creating your order!"
      render :new
    end
  end



The end:
#app/controllers/transactions_controller.rb
def create
    CompletePurchase.new(current_user, current_order, current_restaurant).create(updated_params,
      ->(restaurant, transaction) {
        session[:current_order] = nil
        flash[:notice] = "Successfully created your order!"
        redirect_to restaurant_transaction_path(restaurant, transaction)
      },
      -> {
        flash[:notice] = "There was a problem creating your order!"
        render :new
    })
  end
  
#app/use_cases/complete_purchase.rb
class CompletePurchase

  def initialize(user, order, restaurant, mailer=OrderMailer)
    @user = user
    @order = order
    @restaurant = restaurant
    @mailer = mailer
  end

  def create(params, success, failure)
    ActiveRecord::Base.transaction do
      transaction = Transaction.new(params)
      if transaction.save
        transaction_successfully_saved(transaction)
        success.call(@restaurant, transaction)
      else
        failure.call
      end
    end
  end

  def transaction_successfully_saved(trans)
    @order.update(:user_id => @user.id) if @user
    @mailer.order_confirmation(trans).deliver
  end

end