type object 'TransitionApproval' has no attribute '_mptt_meta'

[ahmedalrifai]

Hello to all 👋, great package u have here hope us fix this problem soon

When i try to access TransitionApproval add page in admin it tells me that there is no _mptt_meta atrr

I think to fix it u must let TransitionApproval inherit from mptt.models.MPTTModel

This is my Tracback

Environment:

Request Method: GET
Request URL: http://127.0.0.1:8000/admin/river/transitionapproval/add/

Django Version: 2.2.17
Python Version: 3.8.10
Installed Applications:
['django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'corsheaders',
 'rest_framework',
 'django_filters',
 'drf_spectacular',
 'django_jsonfield_backport',
 'django_celery_results',
 'django_celery_beat',
 'channels',
 'behave_django',
 'river',
 'mptt',
 'core',
 'users',
 'chat',
 'task_management']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'whitenoise.middleware.WhiteNoiseMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'corsheaders.middleware.CorsMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware']

Traceback:

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\core\handlers\exception.py" in inner
  34.             response = get_response(request)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\core\handlers\base.py" in _get_response
  115.                 response = self.process_exception_by_middleware(e, request)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\core\handlers\base.py" in _get_response
  113.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\options.py" in wrapper
  606.                 return self.admin_site.admin_view(view)(*args, **kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\utils\decorators.py" in _wrapped_view
  142.                     response = view_func(request, *args, **kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\views\decorators\cache.py" in _wrapped_view_func
  44.         response = view_func(request, *args, **kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\sites.py" in inner
  223.             return view(request, *args, **kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\options.py" in add_view
  1645.         return self.changeform_view(request, None, form_url, extra_context)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\utils\decorators.py" in _wrapper
  45.         return bound_method(*args, **kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\utils\decorators.py" in _wrapped_view
  142.                     response = view_func(request, *args, **kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\options.py" in changeform_view
  1529.             return self._changeform_view(request, object_id, form_url, extra_context)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\options.py" in _changeform_view
  1562.         ModelForm = self.get_form(request, obj, change=not add)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\options.py" in get_form
  669.             fields = flatten_fieldsets(self.get_fieldsets(request, obj))

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\options.py" in get_fieldsets
  330.         return [(None, {'fields': self.get_fields(request, obj)})]

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\options.py" in get_fields
  321.         form = self._get_form_for_get_fields(request, obj)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\options.py" in _get_form_for_get_fields
  659.         return self.get_form(request, obj, fields=None)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\options.py" in get_form
  705.             return modelform_factory(self.model, **defaults)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\forms\models.py" in modelform_factory
  551.     return type(form)(class_name, (form,), form_class_attrs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\forms\models.py" in __new__
  251.             fields = fields_for_model(

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\forms\models.py" in fields_for_model
  176.             formfield = formfield_callback(f, **kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\options.py" in formfield_for_dbfield
  156.                 formfield = self.formfield_for_foreignkey(db_field, request, **kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\contrib\admin\options.py" in formfield_for_foreignkey
  243.         return db_field.formfield(**kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\mptt\fields.py" in formfield
  34.         return super(TreeOneToOneField, self).formfield(**kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\db\models\fields\related.py" in formfield
  1022.         return super().formfield(**kwargs)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\db\models\fields\related.py" in formfield
  952.         return super().formfield(**{

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\db\models\fields\related.py" in formfield
  419.         return super().formfield(**defaults)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\django\db\models\fields\__init__.py" in formfield
  897.         return form_class(**defaults)

File "C:\Users\Ahmed Alrifai\Projects\portfoliopro\backend\venv\lib\site-packages\mptt\forms.py" in __init__
  29.             mptt_opts = queryset.model._mptt_meta

Exception Type: AttributeError at /admin/river/transitionapproval/add/
Exception Value: type object 'TransitionApproval' has no attribute '_mptt_meta'

[AngelLiang]

hi, I have the same problem, and I have solved as follow:

create TransitionApprovalForm to exclude previous field and add to TransitionApprovalAdmin

from django.contrib import admin
from django import forms
from river.models.transitionapproval import TransitionApproval

class TransitionApprovalForm(forms.ModelForm):
    class Meta:
        model = TransitionApproval
        exclude = ('previous',)

class TransitionApprovalAdmin(admin.ModelAdmin):
    ...
    form = TransitionApprovalForm