delegate.rb

require 'delegate'
class User
end

class UserDecorator
  def initialize(user)
    @user = user
  end
end

class UserDelegator < SimpleDelegator
end

class UserClassDelegator < DelegateClass(User)
end

u = UserDecorator.new(User.new)
u.class
u = UserDelegator.new(User.new)
u.class
u = UserClassDelegator.new(User.new)
u.class