#25143: ArrayField should implement from_db_value()
----------------------------------+--------------------------------------
Reporter: Odahi | Owner:
Type: Bug | Status: new
Component: contrib.postgres | Version: 1.8
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Changes (by Odahi):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Old description:
> I'm using a custom field with the new Postgres {{{ArrayField}}}:
>
> {{{
>
> class Tag(object):
> def __init__(self, id):
> self.id = id
>
> def __unicode__(self):
> return U"Tag(%d)" % self.id
>
> class TagField(models.SmallIntegerField):
> # Dummy wrapper over SmallIntegerField.
>
> def from_db_value(self, value, expression, connection, context):
> if value is None:
> return value
> return Tag(int(value))
>
> def get_prep_value(self, value):
> return value
> ...
>
> # models.py
>
> class Recommendation(models.Model):
> tags = ArrayField(TagField(), size=3)
>
> def __unicode__(self):
> return self.tags
> }}}
>
> Then
>
> {{{
> >>> Recommendation.objects.create(tags=[Tag(1), Tag(2)])
> >>> Recommendation.objects.all()
>
> [<Recommendation: [1, 2]>] # WRONG
>
> }}}
>
> But this is wrong because I got Integers instead of Tag objects:
>
> {{{
> [<Recommendation: [Tag(1), Tag(2)]>] # OK
> }}}
>
> Looking at the {{{ArrayField}}} source code seems that {{{to_python()}}}
> is implemented but never called. I think {{{from_db_value()}}} should be
> also implemented.
New description:
I'm using a custom field with the new Postgres {{{ArrayField}}}:
{{{
class Tag(object):
def __init__(self, id):
self.id = id
def __unicode__(self):
return U"Tag(%d)" % self.id
class TagField(models.SmallIntegerField):
# Dummy wrapper over SmallIntegerField.
def from_db_value(self, value, expression, connection, context):
if value is None:
return value
return Tag(int(value))
def get_prep_value(self, value):
return value
...
# models.py
class Recommendation(models.Model):
tags = ArrayField(TagField(), size=3)
def __unicode__(self):
return self.tags
}}}
Then
{{{
>>> Recommendation.objects.create(tags=[Tag(1), Tag(2)])
>>> Recommendation.objects.all()
[<Recommendation: [1, 2]>] # WRONG
}}}
This is wrong because I got Integers instead of Tag objects:
{{{
[<Recommendation: [Tag(1), Tag(2)]>] # OK
}}}
Looking at the {{{ArrayField}}} source code seems that {{{to_python()}}}
is implemented but never called. I think {{{from_db_value()}}} should be
also implemented.
--
--
Ticket URL: <https://code.djangoproject.com/ticket/25143#comment:1>
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