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import json
from django import forms
from django.core.exceptions import ValidationError
from django.utils import six
from django.utils.translation import ugettext_lazy as _
__all__ = ['HStoreField']
class HStoreField(forms.CharField):
"""
A field for HStore data which accepts dictionary JSON input.
"""
widget = forms.Textarea
default_error_messages = {
'invalid_json': _('Could not load JSON data.'),
'invalid_format': _('Input must be a JSON dictionary.'),
}
def prepare_value(self, value):
if isinstance(value, dict):
return json.dumps(value)
return value
def to_python(self, value):
if not value:
return {}
if not isinstance(value, dict):
try:
value = json.loads(value)
except ValueError:
raise ValidationError(
self.error_messages['invalid_json'],
code='invalid_json',
)
if not isinstance(value, dict):
raise ValidationError(
self.error_messages['invalid_format'],
code='invalid_format',
)
# Cast everything to strings for ease.
for key, val in value.items():
value[key] = six.text_type(val)
return value
def has_changed(self, initial, data):
"""
Return True if data differs from initial.
"""
# For purposes of seeing whether something has changed, None is
# the same as an empty dict, if the data or initial value we get
# is None, replace it w/ {}.
initial_value = self.to_python(initial)
return super(HStoreField, self).has_changed(initial_value, data)
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