February 25, 2010
How to Store Arbitrary Data in a Django Model
My solution was to serialize/deserialize in and out of JSON using simplejson and a Field class that derives from a TextField. i think it is easier to just read the code and the example of how to use it in the gist below than for me to continue with my rambles.
The Code
from django.db import models from django.utils import simplejson as json from django.conf import settings from datetime import datetime class JSONEncoder(json.JSONEncoder): def default(self, obj): if isinstance(obj, datetime): return obj.strftime('%Y-%m-%d %H:%M:%S') elif isinstance(obj, datetime.date): return obj.strftime('%Y-%m-%d') elif isinstance(obj, datetime.time): return obj.strftime('%H:%M:%S') return json.JSONEncoder.default(self, obj) class JSONField(models.TextField): def _dumps(self, data): return JSONEncoder().encode(data) def _loads(self, str): return json.loads(str, encoding=settings.DEFAULT_CHARSET) def db_type(self): return 'text' def pre_save(self, model_instance, add): value = getattr(model_instance, self.attname, None) return self._dumps(value) def contribute_to_class(self, cls, name): self.class_name = cls super(JSONField, self).contribute_to_class(cls, name) models.signals.post_init.connect(self.post_init) def get_json(model_instance): return self._dumps(getattr(model_instance, self.attname, None)) setattr(cls, 'get_%s_json' % self.name, get_json) def set_json(model_instance, json): return setattr(model_instance, self.attname, self._loads(json)) setattr(cls, 'set_%s_json' % self.name, set_json) def post_init(self, **kwargs): if 'sender' in kwargs and 'instance' in kwargs: if kwargs['sender'] == self.class_name and hasattr(kwargs['instance'], self.attname): value = self.value_from_object(kwargs['instance']) if (value): setattr(kwargs['instance'], self.attname, self._loads(value)) else: setattr(kwargs['instance'], self.attname, None) class SampleModel(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) data = JSONField(null=True, blank=True) sample = SampleModel(first_name='Patrick', last_name='Altman') sample.data = {'pets': None, 'children': ['Benjamin', 'Clare', 'Joshua'], 'some_date': datetime(2010, 02, 01)} sample.save()
UPDATE: It wasn't clear in this post. This wasn't my code, as I had previously pointed out. Just wanted to be clear that I have found this solution useful and have used the snippet so much that I feel like it's mine -- but it's not. :)