On Mon, Oct 24, 2011 at 4:21 PM, Kayode Odeyemi <[email protected]> wrote:
> On Mon, Oct 24, 2011 at 2:57 PM, Tom Evans <[email protected]> wrote:
>>
>> On Mon, Oct 24, 2011 at 11:14 AM, Kayode Odeyemi <[email protected]>
>> wrote:
>> > Hello all,
>> >
>> > class BranchModelChoiceField(ModelChoiceField):
>> > def label_from_instance(self, obj):
>> > return obj
>> >
>> > class TransactionUpdateForm(forms.ModelForm):
>> > branchqs = Branch.objects.values_list(u'name_branch', flat=True) #
>> > use
>> > flat=True if values_list is called with a single field
>> > branch_name = BranchModelChoiceField(branchqs)
>> > class Meta:
>> > model = Transaction
>> > fields = ('teller_no', 'paid')
>>
>>
>> Two things here. ModelChoiceField wants a real queryset, not a
>> ValuesQuerySet. The values of the model choice field should be the
>> primary keys of the model being chosen, which is not the case here
>> (which is why it fails).
>>
>> The second thing is that queryset is evaluated precisely once, when
>> the form is instantiated for the first time. When you add a branch, it
>> will not appear in that form until the server is restarted.
>>
>> Judging from your other reply, you don't actually want a foreign key
>> link to the branch, you simply want to store the name of the branch on
>> the transaction? If so, you should simply declare a ChoiceField and
>> supply it with choices derived from Branch.
>>
>> Eg:
>>
>> class TransactionUpdateForm(forms.ModelForm):
>> branch_name = ChoiceField(required=True)
>> def __init__(self, *args, **kwargs):
>> super(TransactionUpdateForm, self).__init__(*args, **kwargs)
>> self.fields['branch_name'].choices =
>> Branch.objects.all().values('name_branch', 'name_branch')
>>
> Thanks for writing in Tom.
>
> I think what you did is the same as:
>
> class TransactionUpdateForm(forms.ModelForm):
> branchqs = Branch.objects.values_list('bid', u'name_branch')
> branch_name = BranchModelChoiceField(branchqs)
No! It really isn't.
1) In my one the queryset is created inside the form's __init__
method, so it gets executed correctly every time the form is
instantiated. In yours, the queryset is only evaluated once, so has
incorrect values as soon as a branch is added or deleted.
2) If you are using a ModelChoiceField, give it a QuerySet, not a
ValuesListQuerySet - really! This is why you get your unpacking
errors. However, don't you want to store the name of the branch on the
transaction, not the id of the branch? If so, you want a Choice field,
since you are not linking to another object, just denormalizing some
data from it into the Transaction model.
>
> I did try this earlier as well but didn't go to far with it.
>
> But then in the template file, I have {{form.branch_name}} which results
> into "Need more than 1 value to unpack error". How am I expected to print
> the form
> widget (select field) in a template?
>
Assuming you don't give a ModelChoiceField an incorrect value for it's
queryset, it is just this:
{{ form.name_of_field }}
Cheers
Tom
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