Django內置信號問題：使用post_save時出錯

Question

我正在構建一個應用程序，當新的ThreadedComments出現時通知用戶。爲此，我使用post_save信號。這裏是我的models.py：

from django.db import models 
from django.contrib.auth.models import User 
from django.contrib.contenttypes.models import ContentType 
from django.contrib.contenttypes import generic 
from datetime import datetime 

from threadedcomments.models import ThreadedComment 
from django.db.models.signals import post_save 

from blog.models import Post 
from topics.models import Topic 

class BuzzEvent(models.Model): 
    user = models.ForeignKey(User) 
    time = models.DateTimeField(default=datetime.now) 

    content_type = models.ForeignKey(ContentType) 
    object_id = models.PositiveIntegerField() 
    content_object = generic.GenericForeignKey() 

    def __unicode__(self): 
     return self.content_object 

def buzz_on_comment(sender, **kwargs): 
    # This is called when there is a new ThreadedComment 
    comment = kwargs['instance'] 

    user_attr_names = { 
        'post' : 'author', 
        'topic' : 'creator', 
        'tribe' : 'creator', 
       } 

    user = getattr(comment.content_object, 
        user_attr_names[comment.content_type.model]) 

    BuzzEvent.objects.create(content_object=sender, 
          user=user, 
          time=datetime.now()) 

post_save.connect(buzz_on_comment, sender=ThreadedComment) 

的問題是創建一個新的ThreadedComment的時候，我得到一個錯誤：unbound method _get_pk_val() must be called with ThreadedComment instance as first argument (got nothing instead)。 Traceback和調試器表示在創建BuzzEvent對象調用signals.pre_init.send時發生。我現在無法破解django代碼，是否有任何明顯的解決方案或想法？

Answer 1

看起來應該是模型實例（comment是），而不是模型類（sender是）作爲content_object參數：

BuzzEvent.objects.create(content_object=comment, 
         user=user)