I have two models that will use the same CardNumberField() to store credit card numbers. How can I add a custom method to the field to mask the card numbers?
I have created the CardNumberField() which inherits from models.Charfield:
# CARD NUMBER FIELD
class CardNumberField(models.CharField):
description = _('card number')
def __init__(self, *args, **kwargs):
kwargs['max_length'] = 19
super().__init__(*args, **kwargs)
The CardNumberField() is then imported and used in my customers/models.py:
# CARD MODEL
class Card(models.Model):
number = CardNumberField()
...
def __str__(self):
return 'Card [{number}]'.format(number=self.number)
...and in my transactions/models.py:
# TRANSACTION MODEL
class Transaction(models.Model):
card_number = CardNumberField()
...
def __str__(self):
return 'Transaction ...'
So, how can I add the following method to my CardNumberField() to be used by both of my models?
def masked_number(self):
# display masked card number
number = self.number
return number[-4:].rjust(len(number), '#')
Also, how will I grab this field method in a DRF serializer class?
You can override the contribute_to_class method to not only contribute the field, but also include an extra method:
from functools import partialmethod
def _mask_number(self, field):
number = getattr(self, field.attname)
return number[-4:].rjust(len(number), '#')
# CARD NUMBER FIELD
class CardNumberField(models.CharField):
description = _('card number')
def __init__(self, *args, **kwargs):
kwargs['max_length'] = 19
super().__init__(*args, **kwargs)
def contribute_to_class(self, cls, name, **kwargs):
super().contribute_to_class(cls, name, **kwargs)
setattr(
cls, f'masked_{self.name}',
partialmethod(_mask_number, field=self)
)If you add a field foo to a model class, it will automatically add a masked_foo method to that class. This thus also means that if you have two or more CardNumberFields, it will add two or more masked_foo methods.
Use an abstract model instead:
class ModelWithCardNumber(models.Model):
card_number = models.CharField(max_length=19)
@property
def masked_number(self):
return self.card_number[-4:].rjust(len(number), '#')
class Meta:
abstract = True
class Card(ModelWithCardNumber):
def __str__(self):
return 'Card [{number}]'.format(number=self.number)
class Transaction(ModelWithCardNumber):
def __str__(self):
return 'Transaction ...'
Now in your serializer you can access Card.masked_number and Transaction.masked_number.