Hi Tom,
Unfortunately I think our wires are a little crossed. Your response helps
with PUT requests for updates but I still have the validate_category being
called when I am creating a new Question and posting existing categories to
be added to that question with the Question form. If I move the validation
to the save then I can get past the issue. If you picture a form with a
question input box and category multi select filled with existing
categories. Then when I post the question to save a new question, the new
question and existing categories get posted and I then save the question
and apply each category to the question. However because I have a
validate_category method on the CategorySerializer this seems to be called
because I presume it expects that I could be creating new categories at the
same time instead of using existing ones posted? Is there a way around this
issue? I will post the code so you can get a better picture.
<code>
class CategorySerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Category
fields = ('pk', 'category', 'user', 'url')
user = serializers.ReadOnlyField(source='user.username')
def validate_category(self, category):
if self.instance is not None:
#update
category_exists = Category.objects.filter(user=None,
category__iexact=category)
else:
#insert
category_exists =
Category.objects.filter(Q(user=self.context['request'].user) | Q(user=None),
category__iexact=category)
if category_exists:
raise serializers.ValidationError({'category': 'Category %s
already exists.'
% category})
return category
class QuestionSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Question
fields = ('pk', 'question', 'user', 'url', "categories")
categories = CategorySerializer(many=True)
user = serializers.ReadOnlyField(source='user.username')
def create(self, validated_data):
categories = validated_data.pop('categories', None)
question = Question.objects.create(**validated_data)
if categories:
for category in categories:
try:
# Check if user category already exists and use it.
c =
Category.objects.get(user=self.context['request'].user,
**category)
except Category.DoesNotExist:
# Check if default category already exists and use it.
c = Category.objects.get(user=None,
**category)
except Category.DoesNotExist:
# Category does exist, create new one.
c =
Category.objects.create(user=self.context['request'].user,
**category)
question.categories.add(c)
return question
</code>
On Wednesday, 10 August 2016 14:15:53 UTC+2, Tom Christie wrote:
>
> If would inspect `self.instance` in your validate method. If it exists
> then an update is being performed and you can exclude `self.instance.pk`
> from the queryset against which you perform the "does this already exist".
> This way around any validation errors will be checked during the `is_valid`
> call, rather than during `.save()`.
>
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