field_for and nested form with mongoid

Could somebody give me the working example of nested form using mongoid?

My models:

class Employee 
  include Mongoid::Document 
  field :first_name 
  field :last_name 
  embeds_one :address 
end

class Address 
  include Mongoid::Document 
  field :street 
  field :city 
  field :state 
  field :post_code 
  embedded_in :employee, :inverse_of => :address 
end