Ruby DSL

validate.rb

class A
  def self.validates(attribute, options)
    p 'define validator', attribute, options
    @@validatos ||= {}
    @@validatos[attribute] = options
    p '/define validator'
  end

  def valid?
    @@validatos.keys.map do |attribute|
      validate_options = @@validatos[attribute]
      if validate_options[:length]
        validate_length(attribute, validate_options[:length])
      else
        true
      end
    end.reduce(:and)
  end

  def validate_length(attribute, options)
    value = send(attribute)
    value.size > options[:minimum]
  end
end

class B < A
  attr_accessor :foo
  validates :foo, length: { minimum: 2 }

  def initialize(attrs)
    @foo = attrs[:foo]
  end
end

b = B.new(foo: 'a')
p 'Not Valid', b.valid?

b = B.new(foo: 'asda')
p 'Valid', b.valid?