如何在Rails 3中实现"记住我"功能？

rails generate migration AddRememberTokenToUsers remember_token:boolean
rake db:migrate

class User< ActiveRecord::Base
  attr_accessor :remember_me

  before_save :set_remember_token

  private

  def set_remember_token
    if remember_me == "1"
      self.remember_token = true
    end
  end
end

<%= form_for(:session, url: login_path) do |f| %>
  <%= f.label :email %>
  <%= f.text_field :email %>
  <%= f.label :password %>
  <%= f.password_field :password %>
  <%= f.label :remember_me, "记住我" %>
  <%= f.check_box :remember_me %>
  <%= f.submit "登录" %>
<% end %>

class SessionsController< ApplicationController
  def create
    user = User.find_by(email: params[:session][:email].downcase)
    if user && user.authenticate(params[:session][:password])
      if params[:session][:remember_me] == "1"
        cookies.permanent[:remember_token] = user.remember_token
      else
        cookies[:remember_token] = user.remember_token
      end
      redirect_to user
    else
      flash.now[:error] = "邮箱或密码错误"
      render 'new'
    end
  end

  def destroy
    cookies.delete(:remember_token)
    redirect_to root_url
  end
end

class ApplicationController< ActionController::Base
  before_action :remember_user

  private

  def remember_user
    @current_user ||= User.find_by(remember_token: cookies[:remember_token])
  end
end