[英]How to update a related model after another model is created?
I need to automatically update my Account
's amount when a Transaction
is created. 创建
Transaction
我需要自动更新Account
的金额。
I have Transaction
model's model.py
: 我有
Transaction
模型的model.py
:
class Transaction(models.Model):
user = models.ForeignKey(User, default=None)
account = models.ForeignKey(Account, default=None)
...
Its serializers.py
: 它的
serializers.py
:
class TransactionSerializer(serializers.ModelSerializer):
class Meta:
model = Transaction
fields = ('id', 'user', 'account_id', 'category_id', 'name', 'amount', 'description', 'created_at')
def create(self, validated_data):
return Transaction.objects.create(**validated_data)
And its views.py
: 及其
views.py
:
class TransactionList(APIView):
def get(self, request):
user_id = request.user.pk
transactions = Transaction.objects.filter(user_id=user_id).order_by('-created_at')
serializer = TransactionSerializer(transactions, many=True)
return Response(serializer.data)
def post(self, request):
account_id = request.data['account_id']
category_id = request.data['category_id']
serializer = TransactionSerializer(data=request.data)
if serializer.is_valid():
serializer.save(user=request.user, account_id=account_id, category_id=category_id)
self.update_account(request)
return Response(serializer.data, status=HTTP_201_CREATED)
return Response(serializer.errors, status=HTTP_400_BAD_REQUEST)
def update_account(self, request):
account_id = request.data['account_id']
category_id = request.data['category_id']
account = Account.objects.get(pk=account_id)
category = Category.objects.get(pk=category_id)
if category.type == 'expense':
account.amount = (account.amount - int(self.request['amount']))
else:
account.amount = (account.amount + int(self.request['amount']))
# Then what?
I thought of creating a custom method that will be executed within the condition if serializer
is valid, that would get the account and category by their id. 我想创建一个自定义方法,如果
serializer
程序有效,则将在条件内执行该自定义方法,该方法将通过其ID获得帐户和类别。 I could, so far, display the current values they have, such as amount
and name
, but after that, I don't know what to do. 到目前为止,我可以显示它们具有的当前值,例如
amount
和name
,但是在那之后,我不知道该怎么办。 I'm imagining I need to use my AccountSerializer
, but I'm not sure. 我在想我需要使用
AccountSerializer
,但是我不确定。
The easiest way would be to override the save
method of your Transaction
model: 最简单的方法是覆盖
Transaction
模型的save
方法:
class Transaction(models.Model):
user = models.ForeignKey(User, default=None)
account = models.ForeignKey(Account, default=None)
...
def save(self, force_insert=False, force_update=False, using=None, update_fields=None):
super(Transaction, self).save()
# Update self.account
See Django documentation for details. 有关详细信息,请参见Django文档 。
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