See:
http://scottbarnham.com/blog/2008/08/25/dynamic-upload-paths-in-django/

from django.db.models import ImageField, signals


class CustomImageField(ImageField):
    """Allows model instance to specify upload_to dynamically.

    Model class should have a method like:

        def get_upload_to(self, attname):
            return 'path/to/%d' % self.id

    Based on: http://code.djangoproject.com/wiki/CustomUploadAndFilters
    """
    def __init__(self, *args, **kwargs):
        if not 'upload_to' in kwargs:
            kwargs['upload_to'] = 'dummy'
        self.prime_upload = kwargs.get('prime_upload', False)
        if 'prime_upload' in kwargs:
            del(kwargs['prime_upload'])
        super(CustomImageField, self).__init__(*args, **kwargs)

    def contribute_to_class(self, cls, name, **kwargs): 
        """Hook up events so we can access the instance."""
        super(CustomImageField, self).contribute_to_class(cls, name)
        if self.prime_upload:
            signals.post_init.connect(self._get_upload_to, sender=cls)
        signals.pre_save.connect(self._get_upload_to, sender=cls)

    def _get_upload_to(self, instance=None, **kwargs):
        """Get dynamic upload_to value from the model instance."""
        if hasattr(instance, 'get_upload_to'):
            self.upload_to = instance.get_upload_to(self.attname)

    def db_type(self):
        """Required by Django for ORM."""
        return 'varchar(100)'

I have a new short post with an example of how to get dynamic upload paths since the FileStorageRefactor merge. It uses a callable in the upload_to parameter and is much simpler than the method in this post.

See:
Dynamic upload paths in Django

def contribute_to_class(self, cls, name):
“””
Hook up events so we can access the instance.
“””
super(CustomImageField, self).contribute_to_class(cls, name)
if self.prime_upload:
signals.post_init.connect(self._get_upload_to, sender=cls)
signals.pre_save.connect(self._get_upload_to, sender=cls)

def _get_upload_to(self, **kwargs):
“””
Get dynamic upload_to value from the model instance.
“””
instance = kwargs[‘instance’]
if hasattr(instance, ‘get_upload_to’):
self.upload_to = instance.get_upload_to(self.attname)

I’ve just posted an updated version (see above) which should work in this situation.

if form.is_valid():
l = ListingImage()

uploadedImage = form.cleaned_data[‘image’] # an UploadedFile object
l.save_image_file(uploadedImage.filename, uploadedImage.content)

l.caption = form.cleaned_data[‘caption’]
l.sort = form.cleaned_data[‘sort’]
l.save()

ListingImage.image is a CustomImageField()

Anyone know why calling save_image_file() doesn’t invoke the get_upload_to() to save the image to the dynamic path?

Yes, you can. The model that contains the CustomImageField gets to build up the path. Assuming you have a Photo model which has a CustomImageField and is related to a user, you could do something like:

class Photo(models.Model):
    user = models.ForeignKey(User, related_name='photos')
    image = CustomImageField(upload_to='photos')
    creation_date = models.DateTimeField()
    ...
    
    def get_upload_to(self, field_attname):
        return self.user.username

The upload path will be made up of the media path, username and filename. Assuming the username is “ted”, you will get something like: /path/to/media/ted/head.jpg