Django REST framework IntegerField max_length issue - django

Question

I am getting an "__init__() got an unexpected keyword argument 'max_length'" error for my model field of IntegerField with max_length. The stack trace is as follows:
Environment:
Request Method: GET
Request URL: http://localhost:8000/api/jmc/foundation/
Django Version: 1.7.1
Python Version: 2.7.8
Installed Applications:
('django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'dajaxice',
'dajax',
'rest_framework',
'core',
'analytics',
'api')
Installed Middleware:
('django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware')
Traceback:
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response
111. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/views/decorators/csrf.py" in wrapped_view
57. return view_func(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/views/generic/base.py" in view
69. return self.dispatch(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/views.py" in dispatch
406. response = self.handle_exception(exc)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/views.py" in dispatch
403. response = handler(request, *args, **kwargs)
File "/home/dev/Documents/Program Codes/Python/Django/Hera/api/views.py" in get
17. return Response(serializer.data)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in data
547. ret = super(ListSerializer, self).data
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in data
174. self._data = self.to_representation(self.instance)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in to_representation
500. self.child.to_representation(item) for item in iterable
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in to_representation
382. fields = [field for field in self.fields.values() if not field.write_only]
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in fields
245. for key, value in self.get_fields().items():
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in get_fields
911. ret[field_name] = field_cls(**kwargs)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/fields.py" in __init__
597. super(IntegerField, self).__init__(**kwargs)
Exception Type: TypeError at /api/jmc/foundation/
Exception Value: __init__() got an unexpected keyword argument 'max_length'

Answer 1

You might want to use the MaxValueValidator with IntegerField instead of max_length.
from django.db import models
from django.core.validators import MaxValueValidator
class MyModel(models.Model):
number = models.IntegerField(validators=[MaxValueValidator(100)])

Answer 2

Looks like IntegerField in Django doesn't have an max_length option. The reason we don't get any error is because Django suppresses it and 'Django REST framework' doesn't. Just removing the max_length option will make it work again.

Answer 3

Contrary to popular belief and common sense, Django does support the max_length argument on the IntegerField as well as any other field. The error you are seeing here is a known issue with Django REST Framework that does not currently have a fix.
The easiest way to fix this in your serializers (until a fix is done in DRF) is to redefine the field on the serializer without the max_length argument.
class MySerializer(serializers.ModelSerializer):
int_field = serializers.IntegerField()