I have a couple of questions below and would really appreciate some light
on the way to handle the situations described below using the REST
framework where a user can be posting from a web form where we know that we
intend to happen or via a cli where we do no know that the user intends to
happen.
If I have a SerializerClass that has a reference to a m2m (shown below)
1. When a PUT request is sent to update the record and no data for the m2m
relationship was sent with the request should the update method expect that
no data was posted for that m2m so the user intended for them to be
removed. Or does the user expect them to be left in place when not posting
any data for the m2m? I would think the user expects them to be left in
place. But if that is the case, then how would the user signify that he
intends for them to be removed on an update? Should that be handled with a
delete request or a new resource url be created for this purpose?
2. If the user does send data for the m2m relationship in the PUT request
ie a list with one item categories=[{"category":"test"}] are they expecting
the REST api update method update the relationship to only contain the one
element and remove the rest, or are they expecting to keep the existing
records and just add the extra relation?
So should a PUT request be able to delete m2m relations on that record or
should it only be able to ever add to existing relations and a new resource
url should be used to remove the m2m relations?
Example code below.
Thanks
class QuestionSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Question
fields = ('pk', 'question', 'user', 'url', "categories")
categories = CategorySerializer(many=True, required=False)
user = serializers.ReadOnlyField(source='user.username')
def update(self, instance, validated_data):
q = validated_data.get('question', instance.question).strip()
instance.question = q
instance.save()
#1. If an empty list is passed in from a form or cli or no data at
all, does this signify that they should be removed or left in place. If
they should be left alone, do we create a new
#resource url to delete them
#2. If 1 category is passed in a list, does that mean the rest of
the categories get removed and we just add the new one
# or does it mean we leave the categories in place and add the new
one to the existing categories?
categories = validated_data.get('categories')
if categories:
#instance.categories.clear() # should we clear out or not?
for category in categories:
c =
Category.objects.get(Q(user=self.context['request'].user) | Q(user=None),
**category)
instance.categories.add(c)
return instance
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