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Patricio Moracho
Asked: 2020-05-01 20:18:47 +0800 CST 2020-05-01 20:18:47 +0800 CST

What is the difference between using a field validator or validating the model using clean?

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Assuming I have a Django model like the following:

class Comprobante(models.Model):
    punto_venta = models.IntegerField(blank=True)

And I want to validate the model and particularly that punto_ventait is a value from 1 to 9999. I understand that there are two ways:

Use a validator in the field

def punto_venta_validate(value):
    if not value:
        raise ValidationError(_('El punto de venta es obligatorio'))
    if value <1 or value > 9999:
        raise ValidationError(_('El punto de venta debe debe ser un valor entre 1 y 9999'))

class Comprobante(models.Model):
    punto_venta = models.IntegerField(blank=True, validators=[punto_venta_validate]))

Validate on clean()model event

def clean(self):
    punto_venta_validate(self.punto_venta)

The only visible difference is that a ValidationErrorwhen the field is validated by using validators, it will show the message next to the field in the admin interface, when we use clean()to validate, I see that the error appears on all the fields. Eventually clean(), we could also validate multiple conditions and add each error to a list, in this way we could show all the errors of each field, so there would not be a difference between the two methods either. So: What is the difference between both methods? Is it just a matter of how they are displayed ValidationErroror is there something else that I am missing?

python

1 Answers

  1. Best Answer

    Indeed as I mentioned in the comment:

    • The validadoresonly validate the input, they do not return the enhanced format, that is, it cannot be modified. If the input is invalid, it will just output a ValidationError.

    • The methods Clean()validate and return a value that could be a slightly modified value depending on the requirements.

    A validator is simply an object or callable function that takes a value and simply returns nothing if the value is valid or returns a ValidationErrorif it is not. (You find this in the documentation: Here ) The return value is simply ignored.

    If you want to be able to modify the value, you can use the clean_field, in forms as described here .

    Django will first run the built-in field validators (by default), then your custom field validators (using validators=[su_validador]in your models). clean()So, Django will execute the and methods clean<campo>().

    I think one of the main difference between methods validatorand a clean_<campo>()is that the latter is only intended for forms. And the validatorcan be used for both your forms and your models (and will therefore also be used, for example, in the admin interface).

    Also, overriding the method clean_<campo>()is the recommended way to validate data against items in your database.

    Note: You can also apply the same validator to your form fields if you only want it there and not throughout your application.

    Here is an interesting documentation on Validation:

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