Hi Xavier,
Thank you for this info that clears it up for me. I posted another question
regarding manytomany validation the other day that I have not received a
clear response on how to deal with this in the REST framework. Can you
provide some light on the other post when you get chance?
Thanks
On Saturday, 13 August 2016 12:16:45 UTC+2, Jenna Pullen wrote:
>
> 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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