Hello,
thanks for the documentation link, I didn't know that page so far ...
and you were right I should implement get_db_prep_lookup as well.
Right now I the conversion from datetime.datetime to unixtimstamp works
quite well, my only problem is that if access objects from the database
the unixtimestamp is not converted to datetime.datetime.
From my understanging to_python is responsible for that, but it doesn't
even get called if I access foo.timestampfield. Only if I access the
Model in the admin interface _get_val_from_obj gets called.
Here's my current version, perhaps someone can give me a hint were to
convert the unixtimestamp in the database to datetime.datetime, so that
I don't get an int when I access foo.timestampfield.
from django.db.models.fields import DateTimeField, IntegerField, Field
from datetime import datetime
from time import mktime
class TimestampField(DateTimeField, IntegerField):
def get_db_type(self):
return super(IntegerField, self).get_db_type()
def get_internal_type(self):
return super(DateTimeField, self).get_internal_type()
def _get_val_from_obj(self, obj):
return self._from_unixtime(getattr(obj, self.attname))
def get_db_prep_save(self, value):
return super(IntegerField, self).get_db_prep_save(
self._to_unixtime(value))
def _to_unixtime(self, value):
if type(value) is datetime:
value = int(mktime(value.timetuple()))
elif type(value) is str:
value = datetime.strptime(value, "%Y-%m-%d
%H:%M:%S")
value = int(mktime(value.timetuple()))
else:
value = int(value)
return value
def _from_unixtime(self, value):
try:
return datetime.fromtimestamp(float(value))
except Exception, e:
raise e
def get_db_prep_lookup(self, lookup_type, value):
value = self._to_unixtime(value)
return super(IntegerField, self).get_db_prep_lookup(
lookup_type, value)
def to_python(self, value):
print "%s(%s)" % ("to_python", value,)
if value is None:
return value
try:
return datetime.fromtimestamp(value)
except (TypeError, ValueError):#Exception, e:
raise validators.ValidationError(
'%s couldn`t be converted to
datetime' % value)
On Fri, 09 Nov 2007 12:08:23 +1100
Malcolm Tredinnick <[EMAIL PROTECTED]> wrote:
>
> On Thu, 2007-11-08 at 16:40 +0100, Winsley von Spee wrote:
> > Hello,
> >
> > I have implemeted a TimestampField that maps betweem unixtimestamps
> > and datetime.datetime objects, so i can use Datetime in Django
> > while not having to convert all timestamps to datetime fields yet.
> > I need that for downwards compatibility for an old application that
> > uses the same database. The Plan is to use it until I can
> > reimplement the old application in django and afterwards switch to
> > Datetime and DateFields entirely.
> >
> [...]
>
> > Can someone comment wether this is a "proper" approach or wether
> > I'll perhaps experience other problems with this solution?
>
> Have you read [1] and omitted all the other methods you might need
> because you've checked they really aren't needed? For example, usually
> if you write get_db_prep_save(), you need get_db_prep_lookup() as
> well. And, in your case, I'd be tempted to write things so that if
> somebody assigned a datetime to the attribute, instead of a
> timestamp, you changed it in db_prep_save() and changed the attribute
> value as well, so that it's always consistent after a call to save().
>
> A lot of this depends on what you're going to use it for, but have a
> read of the new documentation, if you haven't seen it before, and
> check that you know why you've only implemented those three methods.
>
> [1]
> http://www.djangoproject.com/documentation/custom_model_fields/#useful-methods
>
> Regards,
> Malcolm
>
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