如何在烧瓶中使用g.user全局 [英] How to use g.user global in flask

问题描述

据我了解Flask中的g变量，它应该为我提供一个全局的地方来存放数据，例如登录后保存当前用户。这是正确的吗？

我想我的导航显示我的用户的名字，一旦登录，整个网站。

我的视图包含来自Flask的

  import g #among other things 
  

在登录期间，我分配

  user = User。 query.filter_by（username = form.username.data）.first（）
 if validate（user）：
 session ['logged_in'] = True 
 g.user = user 
  

我似乎无法访问g.user。相反，当我的base.html模板具有以下...

 < ul class =nav> 
 {％if session ['logged_in']％} 
< li class =inactive>以{{g.user.username}}登录< / li> 
 {％endif％} 
< / ul> 
  

我得到错误：

  jinja2.exceptions.UndefinedError 
 UndefinedError：'flask.ctx._RequestGlobals对象'没有属性'user'
  

登录不会正常工作。我缺少什么？

解决方案

g 是一个线程本地，并按请求（请参阅关于代理的说明）。 会话也是本地线程，但是在默认情况下，持久化到MAC签名的cookie并发送到客户端。

您遇到的问题是每个请求都重建 session （因为它被发送到客户端，客户端发回给我们），而设置在 g 上的数据仅适用于这个请求的生命周期。

最简单的事情（注意 simple！= secure - 如果你需要安全的话看看 Flask-Login ）是简单地将用户的ID添加到会话中，并在每个请求上加载用户：

  @ app.before_request 
 def load_user（）：
 if session [user_id]：
 user = User.query.filter_by（username = session [user_id]）。first（）
 else：
 user = {name：Guest}＃使用匿名方法用户改为
 
 gu ser = user 
  

As I understand the g variable in Flask, it should provide me with a global place to stash data like holding the current user after login. Is this correct?

I would like my navigation to display my user's name, once logged in, across the site.

My views contain

from Flask import g #among other things

During login, I assign

user = User.query.filter_by(username = form.username.data).first()
if validate(user):
    session['logged_in'] = True
    g.user = user

It doesn't seem I can access g.user. Instead, when my base.html template has the following...

<ul class="nav">
    {% if session['logged_in'] %}
        <li class="inactive">logged in as {{ g.user.username }}</li>
    {% endif %}
</ul>

I get the error:

jinja2.exceptions.UndefinedError
UndefinedError: 'flask.ctx._RequestGlobals object' has no attribute 'user'

The login otherwise works fine. What am I missing?

解决方案

g is a thread local and is per-request (See A Note On Proxies). The session is also a thread local, but in the default context is persisted to a MAC-signed cookie and sent to the client.

The problem that you are running into is that session is rebuilt on each request (since it is sent to the client and the client sends it back to us), while data set on g is only available for the lifetime of this request.

The simplest thing to do (note simple != secure - if you need secure take a look at Flask-Login) is to simply add the user's ID to the session and load the user on each request:

@app.before_request
def load_user():
    if session["user_id"]:
        user = User.query.filter_by(username=session["user_id"]).first()
    else:
        user = {"name": "Guest"}  # Make it better, use an anonymous User instead

    g.user = user

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