quoted class names in foreign key definition causes 'str' object has no attribute '_default_manager'

[danbrwn]

Myself and another discovered the following error with the code shown. In both cases we had quoted strings for reference class. In both cases importing the specific class and then referencing without the quotes solved the problem. I tried through IRC channel to get a resolution. Downloaded code, wiped out site-packages/django dir before running setup, took other suggestions. Nothing worked except removing the quotes as suggested on the django-users group. I am running Debian Etch final. Python 2.5 and Django 1.0.2, Apache2 with mod_python
AttributeError: 'str' object has no attribute '_default_manager

---

MOD_PYTHON ERROR

ProcessId:      2637
Interpreter:    'TS1.unassigned-domain'

ServerName:     'TS1.unassigned-domain'
DocumentRoot:   '/var/www/'

URI:            '/sipprovision/admin'
Location:       '/sipprovision/'
Directory:      None
Filename:       '/var/www/sipprovision/admin'
PathInfo:       ''

Phase:          'PythonHandler'
Handler:        'django.core.handlers.modpython'

Traceback (most recent call last):

  File "/usr/lib/python2.5/site-packages/mod_python/importer.py", line 1537, in HandlerDispatch
    default=default_handler, arg=req, silent=hlist.silent)

  File "/usr/lib/python2.5/site-packages/mod_python/importer.py", line 1229, in _process_target
    result = _execute_target(config, req, object, arg)

  File "/usr/lib/python2.5/site-packages/mod_python/importer.py", line 1128, in _execute_target
    result = object(arg)

  File "/usr/lib/python2.5/site-packages/django/core/handlers/modpython.py", line 228, in handler
    return ModPythonHandler()(req)

  File "/usr/lib/python2.5/site-packages/django/core/handlers/modpython.py", line 201, in __call__
    response = self.get_response(request)

  File "/usr/lib/python2.5/site-packages/django/core/handlers/base.py", line 67, in get_response
    response = middleware_method(request)

  File "/usr/lib/python2.5/site-packages/django/middleware/common.py", line 56, in process_request
    if (not _is_valid_path(request.path_info) and

  File "/usr/lib/python2.5/site-packages/django/middleware/common.py", line 142, in _is_valid_path
    urlresolvers.resolve(path)

  File "/usr/lib/python2.5/site-packages/django/core/urlresolvers.py", line 246, in resolve
    return get_resolver(urlconf).resolve(path)

  File "/usr/lib/python2.5/site-packages/django/core/urlresolvers.py", line 179, in resolve
    for pattern in self.urlconf_module.urlpatterns:

  File "/usr/lib/python2.5/site-packages/django/core/urlresolvers.py", line 198, in _get_urlconf_module
    self._urlconf_module = __import__(self.urlconf_name, {}, {}, [''])

  File "/var/www/sipprovision/urls.py", line 2, in <module>
    from extensions.models import Extension

  File "/var/www/sipprovision/extensions/models.py", line 42, in <module>
    class ExtensionForm(ModelForm):

  File "/usr/lib/python2.5/site-packages/django/forms/models.py", line 195, in __new__
    opts.exclude, formfield_callback)

  File "/usr/lib/python2.5/site-packages/django/forms/models.py", line 162, in fields_for_model
    formfield = formfield_callback(f)

  File "/usr/lib/python2.5/site-packages/django/forms/models.py", line 177, in <lambda>
    lambda f: f.formfield())

  File "/usr/lib/python2.5/site-packages/django/db/models/fields/related.py", line 694, in formfield
    'queryset': self.rel.to._default_manager.complex_filter(

AttributeError: 'str' object has no attribute '_default_manager'


------------------------- with this model -------------------------------------
from django.db import models
from sipconfig import *
from django.forms import ModelForm, fields, TextInput, IntegerField
# Create your models here.
class Plc(models.Model):
    name=models.CharField(max_length=30)
    ip_addr=models.IPAddressField()
    ip_port=models.IntegerField(default=9600)
    plc_net=models.IntegerField()
    plc_node=models.IntegerField()
    plc_unit=models.IntegerField()

    def __unicode__(self):
          return self.name

    class Admin: pass
 
class VoipGateway(models.Model):
    name=models.OneToOneField('sipconfig.station')
    def __unicode__(self):
          return self.name.dev_name
    class Admin: pass
    
class Extension(models.Model):
    PREFIX_CHOICE=(
        ('1','station'),
        ('9','lock'),
        ('8','voicemail'))
    context=models.ForeignKey('sipconfig.station')
    plc_sys=models.ForeignKey(Plc)
    gateway=models.ForeignKey(VoipGateway)
    word=models.IntegerField()
    bit=models.IntegerField()
    prefix=models.CharField(max_length=2,choices=PREFIX_CHOICE)
    ph_number=models.CharField(max_length=8)
    
    def __unicode__(self):
          return self.context.dev_name +'-'+ self.ph_number

    class Admin: pass

class ExtensionForm(ModelForm):
    class Meta:
       model = Extension
            
        
class ExtAddToContextForm(ModelForm):
    word_increment=IntegerField(widget=TextInput,initial=0)
    bit_increment=IntegerField(widget=TextInput,initial=0)
    phone_increment = IntegerField(widget=TextInput,initial=0)
    class Meta:
        model = Extension
class PlcForm(ModelForm):
    class Meta:
        model=Plc
class VoipGatewayForm(ModelForm):
    class Meta:
        model=VoipGateway
-------------------------------- with this admin.py -------------------------------
from sipprovision.extensions.models import Plc,VoipGateway,Extension
from django.contrib import admin
class ExtensionAdmin(admin.ModelAdmin):
    list_display=('context','plc_sys','gateway','word','bit','prefix','ph_number')
    list_filter=('plc_sys','prefix')
class PlcAdmin(admin.ModelAdmin):
    list_display=('name','ip_addr','ip_port','plc_node','plc_net','plc_unit')
admin.site.register(Plc,PlcAdmin)
admin.site.register(VoipGateway)
admin.site.register(Extension,ExtensionAdmin)

------------------- LINE in related.py returning error is ------------------------
 def formfield(self, **kwargs):
        defaults = {
            'form_class': forms.ModelChoiceField,
            'queryset': self.rel.to._default_manager.complex_filter(
                                                    self.rel.limit_choices_to),
            'to_field_name': self.rel.field_name,
        }
        defaults.update(kwargs)
        return super(ForeignKey, self).formfield(**defaults)

[Alex Gaynor]

Pleas use the preview button. Further this is tested quite extensively: ​http://code.djangoproject.com/browser/django/trunk/tests/regressiontests/string_lookup/models.py so if no more details can be provided I'm going to mark worksforme.