如何从 Jinja2 模板文档中的 Flask-SQLAlchemy 查询对象访问属性？

Question

成功登录后，我将 user 对象（来自查询）保存到 session 字典中。

当我尝试在我的 Jinja 模板中访问对象的属性时，我得到一个错误。

以下是受影响部分的代码：

Python“views.py”文件：

session['in_session'] = True
session['active_user'] = user

Jinja2“base.html”文件：

{% if session.in_session %}
    <li><a href="">Signed in as {{session.active_user.username|safe|title}}!</a></li>
{%endif%}    

---

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EDIT-1：
这是错误traceback：

TypeError

TypeError：不是 JSON 可序列化的 Traceback（最近一次通话最后一次）

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/flask/app.py", line 1836, in __call__

return self.wsgi_app(environ, start_response)

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/flask/app.py", line 1820, in wsgi_app

response = self.make_response(self.handle_exception(e))

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/flask/app.py", line 1403, in handle_exception

reraise(exc_type, exc_value, tb)

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app

response = self.full_dispatch_request()

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/flask/app.py", line 1479, in full_dispatch_request

response = self.process_response(response)

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/flask/app.py", line 1693, in process_response

self.save_session(ctx.session, response)

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/flask/app.py", line 837, in save_session

return self.session_interface.save_session(self, session, response)

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/flask/sessions.py", line 326, in save_session

val = self.get_signing_serializer(app).dumps(dict(session))

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/itsdangerous.py", line 537, in dumps

payload = want_bytes(self.dump_payload(obj))

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/itsdangerous.py", line 809, in dump_payload

json = super(URLSafeSerializerMixin, self).dump_payload(obj)

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/itsdangerous.py", line 522, in dump_payload

return want_bytes(self.serializer.dumps(obj))

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/flask/sessions.py", line 85, in dumps

return json.dumps(_tag(value), separators=(',', ':'))

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/flask/json.py", line 126, in dumps

rv = _json.dumps(obj, **kwargs)

File "/usr/lib/python2.7/json/__init__.py", line 250, in dumps

sort_keys=sort_keys, **kw).encode(obj)

File "/usr/lib/python2.7/json/encoder.py", line 209, in encode

chunks = list(chunks)

File "/usr/lib/python2.7/json/encoder.py", line 434, in _iterencode

for chunk in _iterencode_dict(o, _current_indent_level):

File "/usr/lib/python2.7/json/encoder.py", line 408, in _iterencode_dict

for chunk in chunks:

File "/usr/lib/python2.7/json/encoder.py", line 442, in _iterencode

o = _default(o)

File "/home/acetakwas/web_dev/flask/flask_venv/lib/python2.7/site-packages/flask/json.py", line 83, in default

return _json.JSONEncoder.default(self, o)

File "/usr/lib/python2.7/json/encoder.py", line 184, in default

raise TypeError(repr(o) + " is not JSON serializable")

TypeError: <User 2: u'tak'; u'ace@tak.was'> is not JSON serializable

---

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EDIT-2：
我刚刚发现问题在于将从我的查询返回的 user 对象存储为字典值。因此，假设我有一个扩展 Model 的 User 类（来自 SQLAlchemy 库），这样做会失败：

session['active_user'] = User.query.filter_by(username='my_user_name').first()

这是为什么呢？

Answer 1

发布您遇到的错误会很有帮助。但如果我不得不猜测，你说 session 是一个字典。在您的代码中，您正在像访问对象一样访问会话。你应该能够简单地做到：

{{session['active_user'].username|safe|title}}