我在accounts/signals/__init__.py中有以下代码：
from django.db.models.signals import post_save
from django.dispatch import receiver
from orders.models import Order
from accounts.models import Balance
@receiver(post_save, sender=Order)
def update_referral_balance(sender, **kwargs):
if len(sender.user.referrals_set.all()):
# TODO: Add referralTransaction
new_referral_revenue = sender.user.referrals_set.get().revenue
revenue_from_trade = \
new_referral_revenue - sender.old_referral_revenue
balance, created = \
Balance.objects.get(user=sender.user, currency=sender.currency)
balance.balance += revenue_from_trade
balance.save()
现在，在运行测试时，我得到以下内容
error:======================================================================
ERROR: test_orders_with_approved_payments (payments.tests.test_views.PaymentReleaseTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/pipeline/source/payments/tests/test_views.py", line 75, in setUp
self.order.save()
File "/pipeline/source/orders/models.py", line 63, in save
super(Order, self).save(*args, **kwargs)
File "/usr/local/lib/python3.5/site-packages/safedelete/models.py", line 64, in save
super(Model, self).save(**kwargs)
File "/usr/local/lib/python3.5/site-packages/django/db/models/base.py", line 708, in save
force_update=force_update, update_fields=update_fields)
File "/usr/local/lib/python3.5/site-packages/django/db/models/base.py", line 745, in save_base
update_fields=update_fields, raw=raw, using=using)
File "/usr/local/lib/python3.5/site-packages/django/dispatch/dispatcher.py", line 192, in send
response = receiver(signal=self, sender=sender, **named)
File "/pipeline/source/accounts/signals/__init__.py", line 9, in update_referral_balance
if len(sender.user.referral_set.all()):
AttributeError: 'ForwardManyToOneDescriptor' object has no attribute 'referral_set'
事实上，在调试器中运行它时，我发现sender.user属性是实例ForwardManyToOneDescriptor：
ipdb> pprint(sender.__dict__['user'].__dict__)
{'cache_name': '_user_cache',
'field': <django.db.models.fields.related.ForeignKey: user>}
我做错了什么？
编辑：我的Order模型：
类Order（TimeStampedModel，SoftDeletableModel，UniqueFieldMixin）： 美元=“美元” RUB =“RUB” EUR =“EUR”
BUY = 1
SELL = 0
TYPES = (
(SELL, 'SELL'),
(BUY, 'BUY'),
)
# Todo: inherit from BTC base?, move lengths to settings?
order_type = models.IntegerField(choices=TYPES, default=BUY)
amount_cash = models.DecimalField(max_digits=12, decimal_places=2)
amount_btc = models.DecimalField(max_digits=18, decimal_places=8)
currency = models.ForeignKey(Currency)
payment_window = models.IntegerField(default=settings.PAYMENT_WINDOW)
user = models.ForeignKey(User, related_name='orders')
is_paid = models.BooleanField(default=False)
is_released = models.BooleanField(default=False)
is_completed = models.BooleanField(default=False)
is_failed = models.BooleanField(default=False)
unique_reference = models.CharField(
max_length=settings.UNIQUE_REFERENCE_LENGTH, unique=True)
admin_comment = models.CharField(max_length=200)
payment_preference = models.ForeignKey('payments.PaymentPreference',
default=None,
null=True)
class Meta:
ordering = ['-created_on']
def save(self, *args, **kwargs):
self.unique_reference = \
self.gen_unique_value(
lambda x: get_random_string(x),
lambda x: Order.objects.filter(unique_reference=x).count(),
settings.UNIQUE_REFERENCE_LENGTH
)
self.convert_coin_to_cash()
if 'is_completed' in kwargs and\
kwargs['is_completed'] and\
not self.is_completed:
self.old_referral_revenue = \
self.user.referral_set.get().revenue
super(Order, self).save(*args, **kwargs)
def convert_coin_to_cash(self):
self.amount_btc = Decimal(self.amount_btc)
queryset = Price.objects.filter().order_by('-id')[:2]
price_sell = [price for price in queryset if price.type == Price.SELL]
price_buy = [price for price in queryset if price.type == Price.BUY]
# Below calculation affect real money the client pays
assert all([len(price_sell),
price_sell[0].price_usd,
price_buy[0].price_rub,
price_buy[0].price_eur])
assert all([len(price_buy),
price_buy[0].price_usd,
price_buy[0].price_rub,
price_buy[0].price_eur])
# TODO: Make this logic more generic,
# TODO: migrate to using currency through payment_preference
# SELL
self.amount_cash = Decimal(self.amount_btc)
if self.order_type == Order.SELL and self.currency.code == Order.USD:
self.amount_cash *= price_buy[0].price_usd
elif self.order_type == Order.SELL and self.currency.code == Order.RUB:
self.amount_cash *= price_buy[0].price_rub
elif self.order_type == Order.SELL and self.currency.code == Order.EUR:
self.amount_cash *= price_buy[0].price_eur
# BUY
if self.order_type == Order.BUY and self.currency.code == Order.USD:
self.amount_cash *= price_sell[0].price_usd
elif self.order_type == Order.BUY and self.currency.code == Order.RUB:
self.amount_cash *= price_sell[0].price_rub
elif self.order_type == Order.BUY and self.currency.code == Order.EUR:
self.amount_cash *= price_sell[0].price_eur
self.amount_cash = money_format(self.amount_cash)
@property
def is_buy(self):
return self.order_type
@property
def payment_deadline(self):
"""returns datetime of payment_deadline (creation + payment_window)"""
# TODO: Use this for pay until message on 'order success' screen
return self.created_on + timedelta(minutes=self.payment_window)
@property
def expired(self):
"""Is expired if payment_deadline is exceeded and it's not paid yet"""
# TODO: validate this business rule
# TODO: Refactor, it is unreasonable to have different standards of
# time in the DB
return (timezone.now() > self.payment_deadline) and\
(not self.is_paid) and not self.is_released
@property
def payment_status_frozen(self):
"""return a boolean indicating if order can be updated
Order is frozen if it is expired or has been paid
"""
# TODO: validate this business rule
return self.expired or \
(self.is_paid and
self.payment_set.last() and
self.payment_set.last().
payment_preference.
payment_method.is_internal)
@property
def withdrawal_address_frozen(self):
"""return bool whether the withdraw address can
be changed"""
return self.is_released
@property
def has_withdraw_address(self):
"""return a boolean indicating if order has a withdraw adrress defined
"""
# TODO: Validate this business rule
return len(self.address_set.all()) > 0
@property
def withdraw_address(self):
addr = None
if self.has_withdraw_address:
addr = self.transaction_set.first().address_to.address
return addr
def __str__(self):
return "{} {} {} BTC {} {}".format(self.user.username or
self.user.profile.phone,
self.order_type,
self.amount_btc,
self.amount_cash,
self.currency)
答案 0 :(得分：4)
sender参数是信号连接到的模型类。正如您在signals docs中看到的那样，在post_save中，实例在一个单独的参数中传递，毫不奇怪地称为instance。
您应该像这样编写处理程序：
@receiver(post_save, sender=Order)
def update_referral_balance(sender, instance, **kwargs):
if len(instance.user.referrals_set.all()):
等，在整个过程中将sender更改为instance。