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POFinding objects according to related objects
 

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    <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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Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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