Refactoring: Refactorings/Introduce Class Annotation

Some methods have become so common that Ruby has the ability to hide them away. These behaviors can be called from the class definition. Note: This should only be done when the purpose behind the methods is clear enough to state in a single word/line.

e.g. attr_reader/writer/accessor

Mechanics

1. Decide on signature of class annotation. Declare it in the appropriate class
2. Convert original method into a class method. Make appropriate changes so that the method works at the class scope.

   Note: Make sure the class method is declared before the class annotation is called

3. Test
4. Consider using Extract Module on the class method to make annotation more prominent in class definitions.
5. Test

Example

Before

class SearchCriteria
  def initialize(hash)
    @author_id = hash[:author_id]
    @publisher_id = hash[:publisher_id]
    @isbn = hash[:isbn]
  end
end

After

module CustomInitializers
  def hash_initializer(*attribute_names)
    define_method(:initialize) do |*args|
      data = args.first || {}
      attribute_names.each do |attribute_name|
        instance_variable_set "@*{attribute_name}", data[attribute_name]
      end
    end
  end
end

Class.send :include, CustomInitializers

class SearchCriteria
  hash_initializer :author_id, :publisher_id, :isbn
end