ruby-on-rails – 尝试使用Koala进行fb apprequest但访问令牌已

另外,我对Facebook文档感到困惑.如果有人能回答我下面的问题,那就太感激了.

> Facebook访问令牌在用户退出Facebook后立即过期,除非它是一个长期存在的令牌？
>假设用户访问令牌已过期.我是否有可能在没有用户A回到我的画布应用程序的情况下获得新的访问令牌？
>当我对用户进行身份验证时,我是否会获得一个短期令牌,然后我可以扩展有效性,如果我想要或者我是否默认获得长期令牌？

下面是我用来使用Koala执行fb请求的代码：

begin
  graph = Koala::Facebook::API.new(access_token)
  graph.put_object("me","apprequests",{:message => "..."})
rescue Koala::Facebook::APIError
  # Assume a user has a short-lived token and hasn't visit my application for a long time. 
  # Is it possible to get a NEW long-lived token here without the user going to my application again 
  # (assume the user did not remove my application) ? If Yes,how to do that using Koala ?
end

谢谢！