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

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.

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