BTW, I am aware of the ability to create your own custom model field
class with a custom `validate()` method like my following example. I'm
also aware of using a model's clean() method to raise logical
validation errors, like if their email is a gmail address and they
they specify that they are a Yahoo user, you might raise
ValidationError("You liar. You use Gmail"), and so on.
My custom field and below an explanation of another pitfall of form
validation:
class CurrencyField(models.DecimalField):
"""
Only changes output into a quantized format. Everything else is
the same.
Later I will possibly add currency symbol support.
"""
description = 'A double decimal representing money'
__metaclass__ = models.SubfieldBase
def __init__(self, *args, **kwargs):
kwargs['max_digits'] = 8
kwargs['decimal_places'] = 2
super(CurrencyField, self).__init__(*args, **kwargs)
def to_python(self, value):
try:
return super(CurrencyField,
self).to_python(value).quantize(Decimal('0.01'))
except AttributeError:
return None
def validate(self, value, model_instance):
"""
Check for anything other than numbers, a decimal, and a dollar
sign, and
raise a singular error on success.
"""
# This allows for a $ symbol as well (but that's not supported
by forms.fields.DecimalField)
reo = re.compile(r'^\$?\s*((?=\d*\.|\d)\d*(?:\.\d*)?)$')
if not reo.search(str(value)):
raise ValidationError(u'Enter a valid "money value"
consisting of digits a single decimal place and an optional dollar
sign.')
super(CurrencyField, self).validate(value, model_instance)
def get_db_prep_value(self, value):
"""
Remove dollar signs.
"""
return re.sub(r'[\d\.]', '', str(value))
The above model does everything necessary but some of it isn't even
use all of the logic with Django forms. If I'm using forms, the user
cannot put a "$" symbol because before my code can possibly normalize
the data and remove the dollar sign, the user is warned about it not
being a decimal. However, decimal is what makes most sense to use, and
I don't want to have to create a custom form for this model just so
that I can strip a dollar sign from one field.
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