http://blog.guiltry.com/everyone-manage-their-object-creation-process-with-factory-pattern

member_controller.rb

class User < ActiveRecord::Base
end

class Knight < User
end

class Archer < User
end

class UserController < ApplicationController
  def create
    @user = User.new(user_params)
    
    if user_params[:type] == "Knight"
      @user.increase_strength(10)
      @user.decrease_agility(4)
    elsif user_params[:type] == "Archer"
      @user.decrease_strength(6)
      @user.increase_agility(8)
    end
  
    # ...
  end
end

class Admin::UserController < ApplicationController
  def create
    @user = User.new(user_params)
    
    if user_params[:type] == "Knight"
      @user.increase_strength(10)
      @user.decrease_agility(4)
    elsif user_params[:type] == "Archer"
      @user.decrease_strength(6)
      @user.increase_agility(8)
    end
  
    # ...
  end
end