Re: updating a single field / attribute, is it possible? or better practices?

[Rock]

In the meantime, creating and executing your own update command is not
difficult.
Here is a snippet for a custom PositionField that updates itself when
necessary with an SQL UPDATE:

http://www.djangosnippets.org/snippets/884/


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Re: updating a single field / attribute, is it possible? or better practices?

[omat]

Exactly. Thanks for the reference.


--
oMat


On Oct 31, 6:54 pm, "Karen Tracey" <[EMAIL PROTECTED]> wrote:
> On Fri, Oct 31, 2008 at 12:39 PM, omat <[EMAIL PROTECTED]> wrote:
>
> > Hi all,
>
> > Is it possible to update a chosen subset of attributes of a model
> > instance?
>
> http://code.djangoproject.com/ticket/4102
>
> asks for this, I believe.
>
> Karen
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Re: updating a single field / attribute, is it possible? or better practices?

[Karen Tracey]

On Fri, Oct 31, 2008 at 12:39 PM, omat <[EMAIL PROTECTED]> wrote:

>
> Hi all,
>
> Is it possible to update a chosen subset of attributes of a model
> instance?
>

http://code.djangoproject.com/ticket/4102

asks for this, I believe.

Karen

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updating a single field / attribute, is it possible? or better practices?

[omat]

Hi all,

Is it possible to update a chosen subset of attributes of a model
instance?

In my case, the view function saves a model instance which was updated
in the model's custom save() method. Thus, the update by the save() is
overridden.


Pseudo code of the scenario:

class MyModel(Model):
qualified = models.BooleanField()
count = models.IntegerField()
def save(self):
self.count = self.refmodel_set.count(qualified=True)
super(...).save()

class RefModel(Model):
my_model = models.ForeignKey(MyModel)

def form_view(request, id):
my_instance = MyModel.objects.get(id=id)
ref_form = RefForm(data)
if ref_form.is_valid():
ref = ref_form.save(commit=False)
ref.my_model = my_instance
ref.save()
if ref.some_attribute:
my_instance.qualified = True
my_instance.save() # this overrides the change made in
MyModel.save()


I thought, if there is a way to save only a single attribute, without
touching others, my problem will be solved. In that case, the last two
lines would look like:

my_instance.qualified = True
my_instance.save(fields=('qualified',))


Does this makes sense?


Thanks for any comments,
oMat

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