CODEWITHSUNDEEP
pythondjango
Robert Price
Robert Price

Reputation: 115

Override Django model field get_prep_value method

When getting a ValueError from a ForeignKey field in Django, the exception returns the response "Field ... expected a a number but got ..." using the field name. I'd like to change this exception to use the verbose_name if it exists, and the field name if it does not. How can I override this exception for all ForeignKey fields?

Line 1818 in https://github.com/django/django/blob/main/django/db/models/fields/__init__.py

    def get_prep_value(self, value):
        value = super().get_prep_value(value)
        if value is None:
            return None
        try:
            return int(value)
        except (TypeError, ValueError) as e:
            raise e.__class__(
                "Field '%s' expected a number but got %r." % (self.name, value),
            ) from e

Upvotes: 0

Views: 748

Answers (1)

Robert Price
Robert Price

Reputation: 115

I ended up getting this custom error message to work by overriding both the IntegerField and AutoField classes.

class CustomIntegerField(models.Field):
    def get_prep_value(self, value):
        value = super().get_prep_value(value)
        if value is None:
            return None
        try:
            return int(value)
        except (TypeError, ValueError) as e:
            field_name = self.name
            if self.verbose_name:
                field_name = self.verbose_name
            raise e.__class__("Custom Error Message") from e

class CustomAutoField(AutoFieldMixin, CustomIntegerField, metaclass=AutoFieldMeta):
    ...

Upvotes: 2

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