#12279: prepare_database_save in add_update_fields makes some custom fields be
impossible.
---------------------------------------------------+------------------------
Reporter: bear330 | Owner: nobody
Status: new | Milestone:
Component: Database layer (models, ORM) | Version: 1.1
Resolution: | Keywords:
prepare_database_save, ObjectField, ClassField
Stage: Unreviewed | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Comment (by bear330):
OK, for the ObjectField and ClassField, I can use it in models like this:
{{{
#!python
# This is just a example, no meaning.
class MyModel(models.Model):
obj = ObjectField()
clz = ClassField()
}}}
{{{
#!python
my = MyModel()
my.obj = User.object.all()[0]
my.clz = User
my.save() # This is OK.
my.obj = User.object.all()[-1] # Change another user.
my.save() # Update it, but it will raise error because User (all models)
has prepare_database_save attribute, so the code in add_update_fields
method (subqueries.py):
# if hasattr(val, 'prepare_database_save'):
# val = val.prepare_database_save(field)
# else:
# val = field.get_db_prep_save(val)
#
# val (user object) will be changed and I can't do anything before that.
# So, I do some hackish in ObjectField above to make this work.
# But for ClassField, this is no good way to do that.
my.clz = Profile
my.save() # It will raise error, because hasattr(val,
'prepare_database_save') is True,
# it will call val = val.prepare_database_save(field)
# then:
# TypeError: unbound method prepare_database_save() must be called with
Profile instance as first argument.
}}}
This is why I said that is impossible do to this kind of custom field.
Thanks!
--
Ticket URL: <http://code.djangoproject.com/ticket/12279#comment:2>
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