formy.rb

require "byebug"

class CharFieldKlass
  def initialize(*args)
  end

  def valid?
  end
end

class Formy
  def self.CharField(*args)
    CharFieldKlass.new(args)
  end

  def valid?
    validations = []

    self.class.instance_variables.each do |name|
      validations << self.class.instance_variable_get(name)
    end

    validations.all? { |validation| validation.valid? }
  end
end

class SurveyForm < Formy
  @name = CharField(required=true)
end

SurveyForm.new.valid?

def create
  form = SurveyForm.(params)
  if form.valid?
    # do something
  else
    render status: :bad_request
  end
end