ImageField is not migrateable with ownwritten migration

[gregorvolkmann]

Hello @francescortiz,

today I tried to migrate my ImageField (django's ImageField) to a seperate class. Unfortunately, the Iterator iterating the objects start's to bother with your ImageCenterFields, even if I don't touch them for my migration:

00XX_migration.py:

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.db import models, migrations

from image.fields import ImageCenterField

def move_placement_images(apps, schema_editor):
    Placement = apps.get_model("core", "Placement")
    PlacementImage = apps.get_model("core", "PlacementImage")

    for placement in Placement.objects.all(): # ITERATOR THROWS HERE
        PlacementImage(image=placement.image, placement=placement).save()

class Migration(migrations.Migration):

    dependencies = [
        ('core', '0013_auto_20150408_1943'),
    ]

    operations = [
        migrations.RunPython(move_placement_images),
    ]

models.py:

[...]
class Placement(models.Model):
    [...]
    image = models.ImageField( # DJANGO'S IMAGEFIELD
        'Image',
        upload_to='placement/',
        height_field='image_height',
        width_field='image_width',
    )
    image_height = models.PositiveIntegerField(
        'Image Height',
        blank=True,
        null=True
    )
    image_width = models.PositiveIntegerField(
        'Image Width',
        blank=True,
        null=True
    )
    image_center = ImageCenterField(
        image_field = image
    )
[...]

image/fields.py, code in question line 85-97:

def post_init_capture(sender, instance, *args, **kwargs):
    fields = instance.__class__._meta.get_all_field_names()
    for field_name in fields:
        try:
            field = instance.__class__._meta.get_field(field_name)
            if isinstance(field, ImageCenterField):
                image_field = instance.__class__._meta.get_field(field.image_field.name)
                image_instance = instance.__getattribute__(image_field.name)
                image_center_instance = instance.__getattribute__(field.name)
                image_instance.__image_center_instance__ = image_center_instance
                image_center_instance.image_path = unicode(image_instance)
        except FieldDoesNotExist:
            pass

Traceback:

Applying core.0014_auto_20150408_1943...Traceback (most recent call last):
File "./manage.py", line 10, in <module>
  execute_from_command_line(sys.argv)
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
  utility.execute()
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/core/management/__init__.py", line 377, in execute
  self.fetch_command(subcommand).run_from_argv(self.argv)
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/core/management/base.py", line 288, in run_from_argv
  self.execute(*args, **options.__dict__)
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/core/management/base.py", line 338, in execute
  output = self.handle(*args, **options)
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 160, in handle
  executor.migrate(targets, plan, fake=options.get("fake", False))
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/db/migrations/executor.py", line 63, in migrate
  self.apply_migration(migration, fake=fake)
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/db/migrations/executor.py", line 97, in apply_migration
  migration.apply(project_state, schema_editor)
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/db/migrations/migration.py", line 107, in apply
  operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/db/migrations/operations/special.py", line 117, in database_forwards
  self.code(from_state.render(), schema_editor)
File "/Users/USER/Desktop/PROJECT/DJANGO/core/migrations/0014_auto_20150408_1943.py", line 12, in move_placement_images
  for placement in Placement.objects.all():
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/db/models/query.py", line 141, in __iter__
  self._fetch_all()
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/db/models/query.py", line 966, in _fetch_all
  self._result_cache = list(self.iterator())
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/db/models/query.py", line 275, in iterator
  obj = model(*row_data)
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/db/models/base.py", line 455, in __init__
  signals.post_init.send(sender=self.__class__, instance=self)
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/django/dispatch/dispatcher.py", line 198, in send
  response = receiver(signal=self, sender=sender, **named)
File "/Users/USER/Desktop/PROJECT/venv/lib/python2.7/site-packages/image/fields.py", line 91, in post_init_capture
  image_field = instance.__class__._meta.get_field(field.image_field.name)
AttributeError: 'NoneType' object has no attribute 'name'

All Placements have images assigned, so none of them are None.

[francescortiz]

This should work.

Placement = apps.get_model("core", "Placement")
Placement._meta.get_field('image_center').image_field = model_class._meta.get_field('image')

I should provide some helper function. Adding it to the TODO

[gregorvolkmann]

Ran into this problem again today. Thanks for the hint, it works. But I think you have forgotten to replace model_class with Placement. A more general example:

ModelClass = apps.get_model("core", "ModelClass")
ModelClass._meta.get_field('image_center').image_field = ModelClass._meta.get_field('image')

[francescortiz]

Thank you for the correction.