example_of_makro.rb

class Validator
  def self.presence(value, *fields)
    puts value
    puts fields
  end
end

class Product

  def self.validates(*params)
      validator_param = params.pop
      validator_name = validator_param.keys.first
      validator_value = validator_param.values.first

      Validator.public_send(validator_name, validator_value, *params)
  end

  validates :name, :first_name, presence: true
end