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POFinding objects according to related objects
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  1. POFinding objects according to related objects
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    copied!<p>I am trying to build a messaging application with Django. The reason I don’t use <code>postman</code> is that I need messaging between other objects than users and I don’t need most of the postman’s features.</p> <p>Here are my models:</p> <pre><code>class Recipient(models.Model): ... def get_unread_threads(): see below... class Thread(models.Model): author = models.ForeignKey(Recipient, related_name='initiated_threads') recipients = models.ManyToManyField( Tribe, related_name='received_thread', through='ThreadReading') subject = models.CharField(max_length=64) class Meta: app_label = 'game' class Message(models.Model): author = models.ForeignKey(Recipient, related_name='sent_messages') date_add = models.DateTimeField(auto_now_add=True) date_edit = models.DateTimeField(blank=True) content = models.TextField(max_length=65535) thread = models.ForeignKey(Thread) class Meta: get_latest_by = 'date' class ThreadReading(models.Model): thread = models.ForeignKey(Thread) recipient = models.ForeignKey(Recipient) date_last_reading = models.DateTimeField(auto_now=True) </code></pre> <p>My problem is about <code>get_unread_threads</code>. I can’t really find out how to do that. Here is a first try:</p> <pre><code>def get_unread_threads(self): """ return a queryset corresponding to the threads which at least one message is unread by the recipient """ try: query = self.received_thread.filter( message__latest__date_add__gt=\ self.threadreading_set.get(thread_id=F('id')).date_last_reading) except ObjectDoesNotExist: query = None return query </code></pre> <p>But obviously it doesn’t work because lookup can’t follow method <code>latest</code>.</p>
 

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