law of demeter and rails delegation

delegate_with_allow_nil.rb

class Order < ActiveRecord::Base
  delegate :name, :price, to: :item, prefix: true, allow_nil: true
  delegate :number, to: :invoice, prefix: true, allow_nil: true
end

delegate_with_prefix.rb

class Order < ActiveRecord::Base
  delegate :name, :price, to: :item, prefix: true
  delegate :number, to: :invoice, prefix: true
end

delegated_view.rb

<%= @order.item_name %>
<%= @order.item_price %>
<%= @order.invoice_number %>

initial_delegate.rb

class Order < ActiveRecord::Base
  delegate :item_name, :item_price, to: :item
  delegate :invoice_number, to: :invoice
end

item_with_wrapper.rb

class Item < ActiveRecord::Base
  def item_name
    name
  end
  def item_price
    price
  end
end

law_of_demeter_fix.rb

user.address_street_name
recipe.igredient_name
car.horse_power

law_of_demeter_violation.rb

user.address.street_name
recipe.igredient.name
car.engine.horse_power

order_with_wrapper.rb

class Order < ActiveRecord::Base
  def item_name
    item.name
  end
  def item_price
    item.price
  end
  def invoice_number
    invoice.number
  end
end

violating_view.rb

<%= @order.item.name %>
<%= @order.item.price %>
<%= @order.invoice.number %>