Re: Validators and django.contrib.postgres.fields JSONField

Ah! Fantastic! I love it when I make a dumb mistake because it's an easy solution!

Instead of:

class DummyModel(models.Model):
    dummyJson = JSONField(validators = [TestValidator])#Using class, wrong!


I should be doing:

class DummyModel(models.Model):
    dummyJson = JSONField(validators = [TestValidator()])#Using instance of class, right!


As for using a class as a validator, I am performing some complex validation on the data inside the JSON to ensure it adheres to a specific format above and beyond the normal JSON validation, so a class based validator seemed like the right way to go. I based this off things like the Regex validator in django.core.validators found here: https://docs.djangoproject.com/en/1.10/_modules/django/core/validators/#RegexValidator. Perhaps this wasn't the right approach?

Thanks for your help!
-Ryan Causey

On Sunday, August 28, 2016 at 3:46:31 AM UTC-7, Daniel Roseman wrote:

On Sunday, 28 August 2016 07:54:47 UTC+1, Ryan Causey wrote:

So I've dug into this a little more, and I've come up with the debugger trace below.

-> dummyModelInstance.full_clean()
  c:\program files\python35\lib\site-packages\django\db\models\base.py(1210)full_clean()
-> self.clean_fields(exclude=exclude)
  c:\program files\python35\lib\site-packages\django\db\models\base.py(1252)clean_fields()
-> setattr(self, f.attname, f.clean(raw_value, self))
  c:\program files\python35\lib\site-packages\django\db\models\fields\__init__.py(592)clean()
-> self.run_validators(value)
  c:\program files\python35\lib\site-packages\django\db\models\fields\__init__.py(544)run_validators()
-> v(value)
> c:\program files\python35\lib\site-packages\django\utils\deconstruct.py(16)__new__()
-> def __new__(cls, *args, **kwargs):
(Pdb) ll
 16  ->         def __new__(cls, *args, **kwargs):
 17                 # We capture the arguments to make returning them trivial
 18                 obj = super(klass, cls).__new__(cls)
 19                 obj._constructor_args = (args, kwargs)
 20                 return obj

For some reason, when run_validators() calls the custom TestValidator, it seems that a TestValidator object is constructed rather than entering the __call__() method of the class. I can't see a reason for this to happen, so what am I doing wrong here?

Thanks,
-Ryan Causey

This isn't anything to do with JSONFields, but your misunderstanding about what callables are and what `__call__` does. That is not a class method, but an instance method; calling a class merely instantiates it (as you should expect). Whatever is passed as a validator is called; if it's a function, it will be executed, if it's an instance, its `__call__` method will be called, but if it's a class it will be instantiated.

I'm not sure why you are passing a class at all here. Normally a validator is a method; if you need a class for some reason then you should pass an *instance* of that class, not the class itself.

-- 

DR.

--
You received this message because you are subscribed to the Google Groups "Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscribe@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at https://groups.google.com/group/django-users.
To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/64097c88-4239-4631-96be-168260fd53b0%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.