On Dec 13, 9:30 pm, DavidA <david.avraami...@gmail.com> wrote:
> I have two models, Trade and Fill. A Trade can have many fills. Fill
> has a FK to Trade:
>
> class Trade(models.Model):
> trade_date = models.DateField(auto_now_add=True, editable=False)
> side = models.CharField(max_length=12, choices=SIDE_CHOICES)
> inst = models.ForeignKey(Inst)
>
> class Fill(models.Model):
> trade = models.ForeignKey(Trade)
> quantity = models.DecimalField(max_digits=12,decimal_places=2)
> price = models.DecimalField(max_digits=13,decimal_places=6)
> fees = models.DecimalField
> (max_digits=10,decimal_places=2,blank=True,null=True)
> counterparty = models.CharField(max_length=12)
> time = models.TimeField()
> note = models.CharField(max_length=200, blank=True, null=True)
>
> I have a web page that shows information about a Trade along with a
> table of all the Fills for that trade. It also includes a form for
> adding new Fills.
>
> The problem I ran into was that in my view function for saving a new
> Fill, I need to have the Trade instance set for the form to validate.
> But it doesn't make sense for the user to edit the Trade since it's
> tied to the one on the page they were viewing, so the default
> ModelChoiceField doesn't work for this case.
>
> Instead I created a custom field that stores the FK Trade id in a
> hidden field and then resolves it back to the actual Trade instance in
> the clean method:
<snip interesting code>
> While this works, it feels like I'm digging into the internals of
> Django too much with the _meta.get_field() and use of rel and queryset
> in the ModelField.
>
> Does anyone see a simpler solution to this? I feel like I'm missing
> something obvious.
>
> Thanks,
> -Dave
Well, this does seem like a bit of overkill for what is after all a
fairly common use case, if I'm understanding you correctly.
Perhaps a better way would be not bother setting the FK value in the
form at all, but to grab it from the request inside the view and use
it there. For example:
def add_fill(request, trade_id):
trade = get_object_or_404(Trade, trade_id)
if request.method == 'POST':
form = AddFillForm(request.POST)
if form.is_valid():
new_fill = form.save(commit=False)
new_fill.trade = trade
new_fill.save()
... etc ...
Does that work for you?
--
DR.
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