value.rb

class Value
  # alias_method is private, wah wah
  singleton_class.send(:alias_method, :old_new, :new)

  def self.new(*fields, &block)
    klass = old_new(*fields, &block)

    klass.instance_eval do
      # Rails' as_json function calls `to_hash` internally and falls back to using `instance_variables`.
      # `instance_variables` returns Value's internal `hash` attribute which we are not interested in.
      alias_method :to_hash, :to_h
    end

    klass
  end
end