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pythondjangomigrationdjango-southautofield

Django South datamigration pre_save() uses model's __unicode__()

My Blog model has AutoSlugField which uses Blog.__unicode__() method.

After data migration all Blog instances have slug set to blog-object-<number> instead of <year>-<month>-<day>. Seems like definition Blog.__unicode__() is ignored.

How could I correctly migrate Blog model?

modelfields.py:

class AutoSlugField(models.CharField):
    def pre_save(self, blog, *args, **kwargs):
        return slugify(unicode(blog))

models.py:

class Blog(models.Model):
    title = models.CharField(max_length=255)
    created = models.DateTimeField(auto_now_add=True)
    slug = AutoSlugField(max_length=50)

    def __unicode__(self):
        return self.created.strftime('%Y-%m-%d')

Migration:

from south.v2 import DataMigration

class Migration(DataMigration):
    def forwards(self, orm):
        for blog in orm.Blog.objects.all():
            blog.title = blog.title.replace('django', 'Django')
            blog.save()
Solution

  • I have updated to South 0.7.6 and used solution from the South documentation. Simply added to_python() and get_prep_value() methods to leave slug field as is.

    class AutoSlugField(models.CharField):
    def pre_save(self, blog, *args, **kwargs):
        return slugify(unicode(blog))

    def to_python(self, value):
        return value

    def get_prep_value(self, value):
        return value