Tengo dos modelos en diferentes aplicaciones así:
class Account(models.Model): """ Class to store fiat account information of a companies bank account """ number = models.CharField(max_length=100) currency = models.ForeignKey(FiatCurrency, on_delete=models.CASCADE) owner = models.ForeignKey(Company, on_delete=models.CASCADE) date_added = models.DateTimeField(auto_now_add=True) def __str__(self): return self.number class FiatTransaction(models.Model): """ Class to store Transactions made between escrow and operative white-listed fiat accounts """ debit_account = models.ForeignKey('company.Account', on_delete=models.CASCADE, related_name='debit_account') credit_account = models.ForeignKey('company.Account', on_delete=models.CASCADE, related_name='credit_account') executed_on = models.DateTimeField(auto_now_add=True) amount = models.FloatField() currency = debit_account.currency is_processed = models.BooleanField(default=False) fee = models.FloatField() memo = models.CharField(max_length=250) def __str__(self): return F"Transferred {self.amount} from {self.debit_account} to {self.credit_account} at {self.executed_on}" Ahora, la currency de campo del modelo FiatTransaction no parece funcionar de la forma en que pretendo que lo haga. Se levanta
AttributeError: el objeto 'ForeignKey' no tiene atributo 'moneda'
# Source model class FiatCurrency(models.Model): """ A model to store Fiat Currencies offered by Finchin to include into cash-pools. """ ISO_Code = models.CharField(max_length=3) name = models.CharField(max_length=50) is_active = models.BooleanField(default=True) def __str__(self): return self.name¿Por qué es eso y cómo hacer que esto funcione?
Puedes hacer una @property que determinará la moneda de ese objeto con:
class FiatTransaction(models.Model): debit_account = models.ForeignKey('company.Account', on_delete=models.CASCADE, related_name='debit_account') credit_account = models.ForeignKey('company.Account', on_delete=models.CASCADE, related_name='credit_account') executed_on = models.DateTimeField(auto_now_add=True) amount = models.FloatField() is_processed = models.BooleanField(default=False) fee = models.FloatField() memo = models.CharField(max_length=250) @property def currency(self): return self.debit_account.currency Sin embargo, esto puede ser ineficiente si tiene que hacer esto para una gran cantidad de FiatTransaction s.
En ese caso, podría ser mejor eliminar la propiedad de la currency y anotar el QuerySet con:
from django.db.models import F FiatTransaction.objects.annotate(currency= F('debit_account__currency') ) Las FiatTransaction que surjan de esto tendrán un atributo adicional llamado .currency que contendrá la .currency de la .debit_account .
Si necesita esto con frecuencia, puede utilizar un Manager que anotará automáticamente cuando acceda a FiatTransaction.objects :
from django.db.models import F class FiatTransactionManager (models.Manager): def get_queryset(self, *args, **kwargs): return super().get_queryset(*args, **kwargs).annotate( currency=F('debit_account__currency') ) class FiatTransaction(models.Model): # … objects = FiatTransactionManager()