#8633: Field default value force to unicode when create custom field.
------------------------------+---------------------------------------------
Reporter: flytwokites | Owner: nobody
Status: new | Milestone:
Component: Database wrapper | Version: SVN
Keywords: | Stage: Unreviewed
Has_patch: 0 |
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When create a custom field like document
"http://www.djangoproject.com/documentation/custom_model_fields/"; does:
{{{
class Hand(object):
def __init__(self, north, east, south, west):
self.north = north
self.east = east
self.south = south
self.west = west
class HandField(...):
...
def to_python(self, value):
...
class Foo(models.Model):
hand = HandField(default=Hand(...))
f = Foo()
# This will use the default hand value, but value passed to
HandField.to_python is string format of hand.
# If we not define a Hand.__str__ function, this string is like '<Hand
instance at 0x????????>'.
# So the HandField.to_python not able to recognize this string value.
# So we must define a __str__ on Hand, and HandField must convert this
string back to Hand instance.
# In some custom field value __str__ output is a human readable text, and
difficult to convert back to a instance.
# So it is better to pass default value direct to to_python().
f.save()
}}}
The code in django/db/models/fields/__init__.py
{{{
class Field:
def get_default(self):
"Returns the default value for this field."
if self.default is not NOT_PROVIDED:
if callable(self.default):
return self.default()
return force_unicode(self.default, strings_only=True)
if not self.empty_strings_allowed or (self.null and not
connection.features.interprets_empty_strings_as_nulls):
return None
return ""
}}}
--
Ticket URL: <http://code.djangoproject.com/ticket/8633>
Django Code <http://code.djangoproject.com/>
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