has_associative_facades

github.com/midas/has_associative_facades/tree/master

DESCRIPTION:

A Rails gem that creates getters and setters for associated object’s attributes to aid in not breaking Demeter’s Law.

WHY

From en.wikipedia.org/wiki/Law_of_Demeter, the “Law of Demeter for Functions/Methods” (LoD-F) states:

An object A can request a service (call a method) of an object instance B, but object A cannot “reach through” object B to access yet another object, C, to request its services. Doing so would mean that object A implicitly requires greater knowledge of object B’s internal structure. Instead, B’s class should be modified if necessary so that object A can simply make the request directly of object B, and then let object B propagate the request to any relevant subcomponents. Or A should have a direct reference to object C and make the call directly. If the law is followed, only object B knows its own internal structure.

In particular, an object should avoid invoking methods of a member object returned by another method. For many modern object oriented languages that use a dot as field identifier, the law can be stated simply as “use only one dot”. That is, the code “a.b.Method()” breaks the law where “a.Method()” does not.

As a simple example, when one wants to walk a dog, it would be folly to command the dog’s legs to walk directly; instead one commands the dog and lets it take care of its legs itself

The advantage of following the Law of Demeter is that the resulting software tends to be more maintainable and adaptable. Since objects are less dependent on the internal structure of other objects, object containers can be changed without reworking their callers.

A disadvantage of the Law of Demeter is that it sometimes requires writing a large number of small “wrapper” methods (sometimes referred to as Demeter Transmogrifiers) to propagate method calls to the components. Furthermore, a class’s interface can become bulky as it hosts methods for contained classes resulting in a class without a cohesive interface.

This is where has_associative_facades steps in. Instead of writing this large number of wrapper methods, you can just call the methods and they will be defined on an as needed basis, remaining in memory until the object is destroyed. So now you can avoid coupling your objects together without the extra work. Only the interface to your object need remain the same. You can change the internal implementation of methods to your heart;s content without breaking your project.

FEATURES:

• Automatically creates facade getter methods for has one and belongs to associations.

TO IMPLEMENT:

• Automatically creates facade setter methods for has one and belongs to associations.

• Possibly provide a static way to define through macro type singleton methods (like attr_accessor, attr_reader, etc).

USAGE:

For:

class Account < ActiveRecord::Base
  # has name attribute
end

class User
  has_associative_facades

  belongs_to :account
end

You can now:

user = User.first # or User.new, User.find, etc
user.account_name # is the same as user.account.name

REQUIREMENTS:

• ActiveRecord

INSTALL:

sudo gem install midas-has_associative_facades

In your Rails environment file:

config.gem 'has_associative_facades'

LICENSE:

(The MIT License)

Copyright © 2009 C. Jason Harrelson (midas)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ‘Software’), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ‘AS IS’, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.