Django rest framework: how to override is_valid on a serializer created with many=True?

[MagnusBrzenk]

I have a puzzling question that I posted to SO -- and would REALLY appreciate some help! Thanks!

[tomchristie]

That's confusing isn't it?

There's a bit of a weird dance when you use many=True, which you can see in the __new__ method here.

The normal class creation is bypassed, and you end up with MySerializer(many=True) being equivalent to ListSerializer(child=MySerializer()).

Your custom is_valid() method will be called on any items in the list rather than on the list itself. I can't quite see how it'd lead to the exact behaviour describing but it might help you figure out how to move forward.

One thing that might help you continue to debug your issue would be to stop calling get_serializer() and instead instantiate the serializer directly in the create method. Then once you've done that, switch from many=True to using the explicit ListSerializer(child...) style instead. (Ie. gradually work towards less magic, and a more explicit bit of code behaviour until you've figured out exactly what's going on)

Hope that helps a little

[MagnusBrzenk]

Thanks very much! I did stumble on the listserializer documentation after posting, and figured that had something to do with it.

I don't have the time/energy to dig into the DRF code to figure out exactly how this dance works but, in any case, after thinking harder about what exactly it is that I want, I realized it makes better sense when creating multiple instances of my model to go through each one within the create method, test the validity of each individual instance (with a separate serializer instance with many=False that uses my overriding is_valid) in order to just filter out the bad ones, rather than try to apply my overriding is_valid to the whole list; i.e. I'd prefer to create the good ones and ignore the bad ones, rather than have everything fail.