On May 15, 5:58 pm, simong <[email protected]> wrote:
> There's probably a very simple answer to this but I can't see it at
> the moment:
>
> This model:
>
> class Product(models.Model):
> user = models.ForeignKey(User, related_name="product_list",
> editable=False)
> productid = models.CharField(max_length=40, blank=True)
> prodname = models.CharField(max_length=255, verbose_name='Product
> name')
> proddesc = models.TextField(blank=True, verbose_name='Description')
> prodtopcat = models.ForeignKey(ProductTopCategory,
> verbose_name='Product Main Category')
> prodsubcat = models.ForeignKey(ProductSubCategory,
> verbose_name='Product Sub Category')
> unit = models.ForeignKey(Units, verbose_name='Unit')
> video = models.ManyToManyField('Video', blank=True,
> verbose_name='Video')
> costperunit = models.DecimalField(max_digits=6, decimal_places=2,
> verbose_name='Cost per unit')
> costperlot = models.DecimalField(max_digits=6, decimal_places=2,
> verbose_name='Cost per lot')
> available = models.BooleanField(default=True)
> featured = models.BooleanField(blank=True, null=True)
>
> is used to generate a ModelForm with two modified fields that enable
> the field 'prodsubcat' to be dynamically populated based on the
> selection of 'prodtopcat'.
>
> class DynamicChoiceField(forms.ChoiceField):
> def clean(self, value):
> return value
>
> class ProductForm(ModelForm):
> prodsubcat = DynamicChoiceField(widget=forms.Select(attrs=
> {'disabled': 'true'}), choices =(('-1', 'Select Top Category'),))
>
> I took this from an item I found on the web. I think setting the
> 'disabled' attribute is all I actually need.
>
> The dynamic lookup is performed using jQuery.getJSON with this view:
>
> def feeds_subcat(request, cat_id):
> from django.core import serializers
> json_subcat = serializers.serialize("json",
> ProductSubCategory.objects.filter(prodcat = cat_id), fields=('id',
> 'shortname', 'longname'))
> return HttpResponse(json_subcat, mimetype="application/javascript")
>
> and the SELECT HTML is generated like this:
>
> options += '<option value="' + j[i].pk + '">' + j[i].fields
> ['longname'] + '</option>';
>
> This all works, but on submitting the form, I get the error 'Cannot
> assign "u'17'": "Product.prodsubcat" must be a "ProductSubCategory"
> instance' where "u'17'" is the option value of id_prodsubcat
>
> What type of variable should I be passing (I assume int) and where
> should I be converting it? In validation, in the pre-save signal, in
> the save signal? Or should I be trying to convert it on the form
> itself? Where is the ForeignKey instance save process documented?
>
To bump this and to add more detail: now, when I attempt to save the
form, I am getting the error 'Cannot assign "u'266'":
"Product.prodsubcat" must be a "ProductSubCategory" instance.' where
266 is the primary key of the ProductSubCategory object selected from
a list that is looked up by the selection of a ProductTopCategory
option as shown in the Product model above. How can I return a
ProductSubCategory instance from the variable at form save time?
Simon
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