I have an django project where there are some apps , and models.py
for each app with some ForiegnKey Fields. like below. for example this is Master_data
app and inside models :
class MaintenanceType(models.Model):
name = models.CharField(max_length=10)
display_name = models.CharField(max_length=100, null = True, blank = True)
def __str__(self):
return self.display_name or self.name
calculator app
model:
class FamilyGroup(models.Model):
name = models.CharField(max_length=10, choices=name_choices)
transaction = models.ForeignKey(Transaction, on_delete=models.CASCADE)
family_type = models.ForeignKey(FamilySituation,
on_delete=models.PROTECT,
null=True,
blank=True)
maintenance_type = models.ForeignKey(
MaintenanceType,
on_delete=models.PROTECT,
limit_choices_to={'name__in': ['Single', 'Couple']},
null=True,
blank=True)
so i have a property function in the FamilyGroup
model :
@property
def maintenance_type_rate(self):
b = self.maintenance_type.display_name
r = MaintenanceTypeRate.objects.filter(
Q(rate__gte=0) & Q(maintenance_type__display_name=b))
for d in r:
return float(d.rate or 0)
im getting an error 'NoneType' object has no attribute 'display_name'
the error occurs at the property function
traceback:
File "/home/abdallaoss/cra-calculator/calculator/models.py", line 301, in maintenance_type_rate
b = self.maintenance_type.display_name or
Exception Type: AttributeError at /calculator/transaction/
Exception Value: 'NoneType' object has no attribute 'display_name'
I tried this :
@property
def maintenance_type_rate(self):
try:
b = self.maintenance_type.display_name
except AttributeError:
b = "No display_name found!"
r = MaintenanceTypeRate.objects.filter(
Q(rate__gte=0) & Q(maintenance_type__display_name=b))
for d in r:
return float(d.rate or 0)
question from:
https://stackoverflow.com/questions/65858778/nonetype-object-has-no-attribute-display-name-in-django 与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…