Disclaimer
This is proof of concept snippet, It can not be considered as best practice. Seems like it's better to store (key => value) in sepetare model with 'key' and 'value' fields.
Example
You can assign any dict to model field that can be dumped/serialized with Django json encoder/decoder. Data is saved as TextField in database, empty dict is saved as empty text. Tested with Django 1.2beta.
import DictionaryField
class UserData(models.Model):
user = models.ForeignKey(User)
meta = DictionaryField(blank=True)
There are similar snippets: JSONField 1 or JSONField 2.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 | #-*- coding: utf-8 -*-
from django import forms
from django.core import exceptions
from django.core.serializers.json import DjangoJSONEncoder
from django.db import models
from django.utils import simplejson
from django.utils.translation import ugettext_lazy as _
class DictionaryField(models.Field):
description = _("Dictionary object")
__metaclass__ = models.SubfieldBase
def get_internal_type(self):
return "TextField"
def to_python(self, value):
if value is None:
return None
elif value == "":
return {}
elif isinstance(value, basestring):
try:
return dict(simplejson.loads(value))
except (ValueError, TypeError):
raise exceptions.ValidationError(self.error_messages['invalid'])
if isinstance(value, dict):
return value
else:
return {}
def get_prep_value(self, value):
if not value:
return ""
elif isinstance(value, basestring):
return value
else:
return simplejson.dumps(value)
def value_to_string(self, obj):
value = self._get_val_from_obj(obj)
return self.get_prep_value(value)
def clean(self, value, model_instance):
value = super(DictionaryField, self).clean(value, model_instance)
return self.get_prep_value(value)
def formfield(self, **kwargs):
defaults = {'widget': forms.Textarea}
defaults.update(kwargs)
return super(DictionaryField, self).formfield(**defaults)
# rules for South migrations tool (for version >= 0.7)
try:
from south.modelsinspector import add_introspection_rules
add_introspection_rules([], ["^carting\.fields\.DictionaryField"])
except ImportError:
pass
|
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Comments
What's up with all the custom model field snippets swallowing exceptions and failing silently in to_python() ?!? In addition this fails by: (1) missing the
__metaclass__ = models.SubfieldBase
and (2) using an inexistent (as of 1.1 at least) models.Field.clean() method.#
gsakkis, thank you for feedback.
snippet was written for and tested with Django 1.2, and that was pointed in description
I've added
__metaclass__
definition and raising validation error into_python()
Actually, I'm trying not using this approach anymore. That worked for me, but than accured that storing key=>value data in field like that is not convinient. I beleive there are cases when it's useful, but it seems they are rare.
#
Great Field ! Very usefull !
#
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