title: Django - How to update a field inside a model save() method?
body: <p>It is possible to update a model field inside the save() method?</p>
  
  <p>models.py:</p>
  
  <pre><code>class BicycleAdItemKind(MPTTModel):
  
      image_file_temp_fullpath = ""
      image_file_temp_filename = ""
  
      def url(self, filename):
          #pdb.set_trace()
  
          #url = "MultimediaData/HelpAdImages/ItemKind/%s/%s" % (self.id, filename)
          url = "MultimediaData/HelpAdImages/ItemKind/Temp/%s" % (filename)
          self.image_file_temp_fullpath = url
          self.image_file_temp_filename = filename
          return url
  
      def item_kind_image(self):
          return '&lt;img align="middle" src="/media/%s" height="60px" /&gt;' % self.image
      item_kind_image.allow_tags = True     
  
      n_item_kind      = models.CharField(max_length=50) # Bicicleta completa, Componentes para bicicleta, Acessorios para ciclista
      parent           = TreeForeignKey('self', null=True, blank=True, related_name='children')
      description      = models.TextField(null=True, blank=True)
      image            = models.ImageField(upload_to=url, null=True, blank=True)
      date_inserted    = models.DateTimeField(auto_now_add=True)
      date_last_update = models.DateTimeField(auto_now=True)
  
      def save(self, *args, **kwargs):
          if not self.id:
              BicycleAdItemKind.tree.insert_node(self, self.parent)
          super(BicycleAdItemKind, self).save(*args, **kwargs)
  
          pdb.set_trace()
          # I will move the file from "Temp" folder to the folder with the "Id" number
          from django.core.files.move import file_move_safe
          src = settings.MEDIA_ROOT + "/" + self.image_file_temp_fullpath 
          dst = settings.MEDIA_ROOT + "/" + "MultimediaData/HelpAdImages/ItemKind/%s/%s" % (self.id, self.image_file_temp_filename)
          new_directory = settings.MEDIA_ROOT + "/MultimediaData/HelpAdImages/ItemKind/%s" % (self.id)
          if not os.path.exists(new_directory):
              os.makedirs(new_directory)
  
              if file_move_safe(src, dst):
                  # I will update the field image
                  BicycleAdItemKind.objects.filter(pk=self.id).update(image=dst)
                  # Delete the Temp file
  
      def __unicode__(self):
          return self.n_item_kind
  
      class MPTTMeta:
          order_insertion_by = ['n_item_kind']
  </code></pre>
  
  <p>The line of code bellow does not do any action,</p>
  
  <pre><code>BicycleAdItemKind.objects.filter(pk=self.id).update(image=dst)
  </code></pre>
  
  <p>It is possible to do an update inside a save method?</p>
  
  <p>Give me some clues.</p>
  
  <p>Best Regards,</p>