The Law of Demeter (LoD), or Principle of Least Knowledge, is a simple design style for developing software with the following guidelines:
- Each unit should have only limited knowledge about other units: only units "closely" related to the current unit.
- Each unit should only talk to its friends; don't talk to strangers.
- Only talk to your immediate friends.
sudo gem install demeter
require "demeter" class User extend Demeter demeter :address attr_accessor :name attr_accessor :address def initialize @address = Address.new end end class Address attr_accessor :country end user = User.new user.address.country = "Brazil" user.address_country #=> Brazil
If you are using ActiveRecord, you don't have to extend the
class User < ActiveRecord::Base has_one :address demeter :address end user = User.first user.address_country
You can easily override a method that has been "demeterized"; just declare it before or after calling the
class User < ActiveRecord::Base has_one :address demeter_address def address_country @address_country ||= address.country.upcase end end
- Allow more than one level
- Automatically create accessors
- Detect all
belongs_torelations and automatically "demeterized" them on ActiveRecord
- Emerson Macedo (http://codificando.com/)
(The MIT License)
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