InheritedClassVar

require 'inherited_class_var'

class Bird
  include InheritedClassVar
  inherited_class_hash :attributes #, shallow: false, reverse: false (default aoptions)
  
  def self.attribute(attribute_name, options={})
    attributes_object.merge(attribute_name.to_sym => options)
  end
  attribute :name, upcase: true
end

class Duck < Bird
  attribute :flying, default: false
end

Bird.attributes # => { name: upcase: true }
Duck.attributes # => { name: upcase: true, flying: false }

gem 'inherited_class_var'

module InheritedClassVar
  class Hash < Variable
    alias_method :merge, :change

    def default_value
      {}
    end

    def _change(hash1, hash2)
      method = options[:shallow] ? :merge! : :deep_merge!
      block = options[:reverse] ? Proc.new {|key,left,right| left }  : Proc.new {|key,left,right| right }
      hash1.public_send(method, hash2, &block)
    end
  end
end

module InheritedClassVar
    def inherited_class_hash(variable_name, options={})
      inherited_class_var variable_name, InheritedClassVar::Hash, options
    end
end