On May 18, 12:02 pm, Simon Greenwood <[email protected]> wrote:
> 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?
To answer myself, this post:
http://monogroncho.com/2008/10/django-gotchas-part-1/
is exactly what I was looking for, although the code as given seems
rather inelegant and gives me the AttributeError 'list' object has no
attribute 'widget'. My feeling is that I don't have to be returning a
list of ProductSubCategory objects, just the one that my choice
represents. Does anyone have a view on this? I can't be the only
person combining django and Ajax in this way.
Simon
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