On Jun 10, 9:42 pm, Adi <[EMAIL PROTECTED]> wrote:
> The application flow works like this: You create a Relation object
> within the context of an Owner Object. There is a rule that says that
> a owner cannot have two Relation with the same pet value. How can I
> create a validation on the form that can check this rule. Basically,
> How can i pass owner object that I have in the view when I call
> RelationForm.is_valid()
A trick I use quite frequently with ModelForms is to require that an
instance is passed to the form on creation::
class RelationForm(ModelForm):
class Meta:
model = Relation
fields = ('pet')
class NoInstance(Exception):
"""Raise this error when an instance
was not passed to the form.
"""
pass
def __init__(self, *args, **kwargs):
super(RelationForm, self).__init__(*args, **kwargs)
# this isn't necessary, but helps remind you that this
# form will expect self.instance.user to exist
if not self.instance or not self.instance.owner:
raise self.NoInstance("You must pass an"\
" instance to this form.")
def clean(self):
try:
Relation.objects.get(
owner=self.instance.owner,
pet=self.cleaned_data.get('pet'))
except Relation.DoesNotExist:
return self.cleaned_data
raise forms.ValidationError(
'You cannot have two of the same pet')
Then in your view, you have to do one of the following::
def my_view(request):
# for a new Relation model:
instance = Relation(user=request.user)
# or for an existing Relation model:
instance = Relation.objects.get(user=request.user)
if request.method == 'POST':
form = RelationForm(request.POST, instance=instance)
if form.is_valid():
...
else:
form = RelationForm(instance=instance)
return render_to_response(...)
Hope that's helpful.
- whiteinge
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