contact_form.rb

class ContactForm < Form
  attr_accessor :name, :email, :message
  validates_presence_of :name, :email, :message

  def save
    # do something
  end
end

form.rb

class Form
  extend ActiveModel::Naming
  extend ActiveModel::Translation
  extend ActiveModel::Callbacks
  include ActiveModel::Validations
  include ActiveModel::Conversion
  
  def initialize(params={})
    params.each_pair do |attr, value|
      self.send(:"#{attr}=", value)
    end unless params.blank?
  end
  
  def new_record?
    true
  end

  def persisted?
    false
  end
  
  def id
    nil
  end
end