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json_field.py
Python
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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()

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