【发布时间】：2016-10-05 02:03:54
【问题描述】：
我正在使用 Google App Engine 和使用 ndb 数据存储的 webapp2 创建一个评论系统。我创建了一个属性 KeyProperty，这样我就可以使用相同的键获取与帖子关联的 cmets。
但是，每当我尝试将帖子的密钥存储到 ndb.KeyProperty 中时，我都会收到一条错误消息。我尝试将 KeyProperty 更改为
p_key= ndb.KeyProperty(Post),
p_key= ndb.KeyProperty(kind="Post"),
p_key= ndb.KeyProperty(kind=Post, repeated=True) but none of these worked.
当我使用带有 ReferenceProperty 的 db 模型时，该应用程序的行为符合我的预期。
这是代码。
def question_key(name = 'default'):
return ndb.Key('questions', name)
class Post(ndb.Model):
question = ndb.StringProperty(required = True)
created = ndb.DateTimeProperty(auto_now_add = True)
last_modified = ndb.DateTimeProperty(auto_now = True)
user = ndb.StringProperty()
def render(self):
self._render_text = self.question.replace('\n', '<br>')
return render_str("post.html", p = self)
class Reply(ndb.Model):
content = ndb.TextProperty(required = True)
p_key= ndb.KeyProperty(kind=Post)
user = ndb.StringProperty()
created = ndb.DateTimeProperty(auto_now_add = True)
last_modified = ndb.DateTimeProperty(auto_now = True)
def render(self):
self._render_text = self.content.replace('\n', '<br>')
return self._render_text
class PostPage(Handler):
def get(self, post_id):
key = ndb.Key('Post', int(post_id), parent=question_key())
post = key.get()
params = dict(post=post)
#retrieve all the comments and then filter it by key
if Reply.query():
reply = Reply.query(Reply.p_key == key)
params['reply'] = reply
if self.user:
params['current_user'] = self.user.name
if not post:
self.error(404)
return
self.render("permalink.html", **params)
def post(self, post_id):
reply_content = self.request.get('reply')
p_key = self.request.get('p_key') #get post key from template
user = self.user
if reply_content:
r = Reply(content=reply_content, p_key=p_key, user=user)
r.put()
self.redirect('/stories/%s' % str(post_id))
else:
error = "error"
self.redirect('/stories/%s' % str(post_id))
class NewPost(Handler):
def get(self):
if self.user:
self.render("newpost.html")
else:
self.redirect("/login")
def post(self):
if not self.user:
self.redirect('/')
question = self.request.get('question')
user=self.user.name
if question:
p = Post(parent = question_key(), question = question, user=user)
p.put()
self.redirect('/stories/%s' % str(p.key.id()))
else:
error = "error"
self.render("newpost.html", error=error)
app = webapp2.WSGIApplication([('/', MainPage),
('/stories/([0-9]+)', PostPage),
('/stories/newpost', NewPost),
],
debug=True)
以下是错误信息。
Traceback (most recent call last):
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1535, in __call__
rv = self.handle_exception(request, response, e)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1529, in __call__
rv = self.router.dispatch(request, response)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1278, in default_dispatcher
return route.handler_adapter(request, response)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1102, in __call__
return handler.dispatch()
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 572, in dispatch
return self.handle_exception(e, self.app.debug)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 570, in dispatch
return method(*args, **kwargs)
File "/Users/young-junpark/kloupod-143223/main.py", line 240, in post
r = Reply(content=reply_content, p_key=p_key, user=user)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/ext/ndb/model.py", line 2947, in __init__
self._set_attributes(kwds)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/ext/ndb/model.py", line 2993, in _set_attributes
prop._set_value(self, value)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/ext/ndb/model.py", line 1145, in _set_value
value = self._do_validate(value)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/ext/ndb/model.py", line 1092, in _do_validate
value = self._call_shallow_validation(value)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/ext/ndb/model.py", line 1284, in _call_shallow_validation
return call(value)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/ext/ndb/model.py", line 1331, in call
newvalue = method(self, value)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/ext/ndb/model.py", line 1781, in _validate
(value,))
BadValueError: Expected string, got User(key=Key('users', 'default', 'User', 5629499534213120), created=datetime.datetime(2016, 10, 4, 23, 12, 27, 1990), email=u'youngtheabsolute@gmail.com', name=u'\ubc15\uc6a9\uc900', pw_hash=u'JsIho,9c9f5b4b3a19213e8a84318db6d2e94179678d2d7f22cce6af9b30a558423b28', verification_code=u'12345', verified=False)
非常感谢您的帮助！
【问题讨论】：
-
看起来
Reply.user是StringProperty，但您传递的是User实例... -
什么是“问题”？对于ndb.Key()，第一个参数应该是扩展ndb.Model() 的另一个类的名称。类通常以大写字母开头，您提供的代码中没有“问题”类，但您在
question_key函数中引用了它。 -
@Jalepeno112 所以它曾经是 def question_key(name = 'default'): return db.Key.from_path('questions', name) 这只是一个虚拟父级，在 db 模型中完美运行.但是当我尝试将其迁移到 ndb 模型时，我开始遇到所有这些错误。原始代码来自我参加的一门课程。父键的解释请看链接discussions.udacity.com/t/…
-
所以我想我已经明白了，但是如果没有完整的错误回溯，这很难。您创建
ndb.Key("Post", post_id, parent=question_key())，然后将其发送到PostPage.get()中的模板。这个键在模板中变成了一个字符串。您将该密钥发送回PostPage.post()。因此，当您尝试使用该键创建Reply时，它无法说它期望ndb.Key而是收到一个看起来像键的字符串。您应该考虑使用urlsafe键。解释了here -
@Jalepeno112 成功了！非常感谢你的帮助！对此，我真的非常感激！我刚刚了解了 db 和 ndb 之间的主要区别。度过一个美好的夜晚！
标签： python google-app-engine google-cloud-datastore webapp2 google-app-engine-python