Write a custom django validation function-CodePudding

I have a field named bar i need to write a validation function to validate this bar in django what conditions can i apply to this and how should my function be?

Note:Please dont share link of django validators

models.py

class Model:
    bar = models.CharField('Bar', max_length=255, blank=True, null=True)

CodePudding user response：

You can define a function that will validate the value and raise a ValidationError [Django-doc] in case the condition is not valid, so:

from django.core.exceptions import ValidationError

def validate_bar(value):
    if not some-condition:
        raise ValidationError('Bar should satisfy a certain condition', code='some_code')

then you add this function to the validators of that field

class MyModel(models.Model):
    bar = models.CharField('Bar', max_length=255, blank=True, null=True, validators=[validate_bar])

note that validators will only run in ModelForms, ModelAdmins, ModelSerializers, etc. Not by the Django ORM for performance reasons.

CodePudding user response：

def val(v):
    if v is not None:
        try:
            if len(v) <= 255:
                return True
        except ValidationError:
            return False

does this work ? with balnk = True ,null = True and max_length