Using the send method. (Refactoring Sales_Engine)

refactor_sales_engine.rb

def self.most_revenue(number_of_results)
  items = get_items_with_appropriate_values(:unit_price)
  sort_and_return_items(items, number_of_results)
end

def self.most_items(number_of_results)
  items = get_items_with_appropriate_values(:quantity)
  sort_and_return_items(items, number_of_results)
end

def self.get_items_with_appropriate_values(value)
  items = Hash.new(0)
  Invoices.find_all_paid_invoices.each do |invoice|
    invoice.invoice_items.each do |inv_item|
      item = Item.find_by_id(inv_item.item_id)
      items[item] += inv_item.send(value)
    end
  end
end

def self.sort_and_return_items(items, number_of_results)
  items.sort_by {|k, v| -v }.map {|hash| hash[0] }.take(number_of_results)
end