one of my model has a field value that needs a default value, such as
class Earnings(models.Model):
earing_num=models.DecimalField(default=)but the setting of the default value depends on a field value of another model
class Product(models.Model):
earning_type=models.CharField() if earning_type is A, the default value is 1
if earning_type _ type is B, the default value is 2
how to achieve
redefine objects and then rewrite the create method
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