get_object() method – what is alternative?

[indigo belfry]

Hello, everyone.
I acutely need a help with my @action functionality.
So, going in details.

1. I have particularly 2 models in my project – Borrowing and Payment (payment for borrowing)
2. I have Stripe gateway payment system, implemented in my project.
3. Now I want to implement logic of refreshing Stripe session url (in case it was expired).
   So, I created the following action inside PaymentViewSet:

@action(
    methods=["POST"],
    detail=True,
    url_path="update_session_url",
)
def recreate_expired_borrowing_session_url(self, request, pk=None):
    borrowing = self.get_object()
    payment = Payment.objects.get(borrowing=borrowing, type="Payment")
    if payment.status == "Expired":
        new_session_for_borrowing = create_stripe_session(
            borrowing=borrowing, request=self.request
        )
        payment.status = "Pending"
        payment.session_id = new_session_for_borrowing.id
        payment.session_url = new_session_for_borrowing.url
        payment.save()
        return Response({"status": "Session url has been updated"})

    return Response({"status": "Session url is still active"})

My current issue is that from very beginning I can’t get Borrowing object using get_object() method
My general assumption as of now is that I can do it moving such action to BorrowingViewSet (I really evidenced that).
But point is that I want to keep this action in PaymentViewSet. And in this case I don’t understand how can I get Borrowing object within PaymentViewSet in other ways than using get_object() method.
Please help me with my issue.
PS. Getting Borrowing object is crucial because based on it I can receive Payment object and do subsequent action with it.

[fierce bloom]

get_object is just a method on the viewset which other methods call. There is nothing inherently special about it. By this I simply mean you could do the query directly as required in your case.
ie borrowing = Borrowing.objects.get(pk=pk)

[indigo belfry]

Hello, Andrew.

I just wanna to say that even in case I follow your suggestion, code also outputs an error

payment.models.Payment.DoesNotExist: Payment matching query does not exist.

I mean - having Borrowing object, I can't even get Payment object by filtration

payment = Payment.objects.get(borrowing=borrowing, type="Payment")

but point is that within my test function I initially create a Borrowing object and subsequently tie it to Payment object

[indigo belfry]

def test_recreate_expired_borrowing_session_url(self):
    # Manually create a new Stripe session for testing purposes
    borrowing = sample_borrowing(user=self.user)
    price_data = stripe.Price.create(
        unit_amount=1200,
        currency="usd",
        product_data={
            "name": f"Payment for borrowing of {self.book_1.title}",
        },
    )
    session = stripe.checkout.Session.create(
        line_items=[
            {
                "price": price_data.id,
                "quantity": 1,
            }
        ],
        mode="payment",
        success_url="http://localhost:8000/success/",
        cancel_url="http://localhost:8000/cancel/",

    )

    payment = sample_payment(
        borrowing=borrowing,
        session_url=session.url,
        session_id=session.id,
        money_to_pay=self.borrowing_1.book.daily_fee
    )
    payment.status = "EX"
    url = reverse('payment:payment-recreate-expired-borrowing-session-url', args=[borrowing.id])
    request = self.factory.post(url)
    request.user = self.user
    new_session = create_stripe_session(borrowing=borrowing, request=request)

    response = self.client.post(url)
    payment.session_id = new_session.id
    payment.session_url = new_session.url

    payment.refresh_from_db()

    # self.assertEqual(response.status_code, status.HTTP_200_OK)
    # self.assertEqual(payment.session_id, new_session.id)
    # self.assertEqual(payment.session_url, new_session.url)
    self.assertEqual(payment.status, "PN")

    self.assertEqual(response.data['status'], "Session url has been updated")

so, it showes that something is wrong maybe on initial step - getting Borrowing object.

[indigo belfry]

well, I mean let's say so

1. In test function everything is correct - I can find Payment by linked Borrowing

2. But inside view - not

[fierce bloom]

Can you share the whole view set?

[indigo belfry]

surely

[indigo belfry]

class PaymentViewSet(
    generics.ListAPIView,
    generics.RetrieveAPIView,
    generics.CreateAPIView,
    viewsets.GenericViewSet
):
    queryset = Payment.objects.all()
    serializer_class = PaymentSerializer
    # permission_classes = (IsAuthenticated,)

    def get_serializer_class(self):
        if self.action == "list":
            return PaymentListSerializer
        if self.action == "retrieve":
            return PaymentDetailSerializer
        return PaymentSerializer

    def get_queryset(self):
        if self.request.user.is_superuser:
            return super().get_queryset()
        print("QUERYSET-T-T-T-T-T-T-T-T", super().get_queryset())
        return super().get_queryset().filter(borrowing__user=self.request.user)

    @action(
        methods=["GET"],
        detail=False,
        url_path="payment_success",
        url_name="success",
    )
    def payment_success(self, request: Request):
        session_id = request.query_params.get("session_id")
        payment = Payment.objects.get(session_id=session_id)

        session = stripe.checkout.Session.retrieve(session_id)
        if session.payment_status == "PD":
            serializer = PaymentSerializer(
                payment, data={"status": "PD"}, partial=True
            )
            serializer.is_valid(raise_exception=True)
            serializer.save()
            return Response(serializer.data, status=status.HTTP_200_OK)
        return Response(status=status.HTTP_400_BAD_REQUEST)

second part

 @action(
        methods=["GET"],
        detail=False,
        url_path="payment_cancel",
        url_name="cancel",
    )
    def payment_cancel(self, request: Request):
        session_id = request.query_params.get("session_id")
        payment = Payment.objects.get(session_id=session_id)
        serializer = PaymentSerializer(payment)
        data = {
            "message": "You can make a payment during the next 2 hours.",
            **serializer.data,
        }
        return Response(data=data, status=status.HTTP_200_OK)

    @action(
        methods=["POST"],
        detail=True,
        url_path="update_session_url",
    )
    def recreate_expired_borrowing_session_url(self, request, pk=None):
        borrowing = Borrowing.objects.get(pk=pk)
        if payment.status == "Expired":
            new_session_for_borrowing = create_stripe_session(
                borrowing=borrowing, request=self.request
            )
            payment.status = "Pending"
            payment.session_id = new_session_for_borrowing.id
            payment.session_url = new_session_for_borrowing.url
            payment.save()
            return Response({"status": "Session url has been updated"})

        return Response({"status": "Session url is still active"})

here is the entire code ofg view

but I talk specifically about last action - recreate session url

[raw trench]

It's a detail URL for a payment object. It needs the Payment's PK in the URL, not the Borrowing's PK

[indigo belfry]

Hello, Ben. What do you mean?

I can filter Payment objects by related Borrowing objects

Nothing wrong with that

If I am not mistaken

[raw trench]

This is a PaymentViewSet. The PK in the URL for detail views is expected to be for a Payment object.

[indigo belfry]

In other way how can I get related object?

I mean the entire process

[raw trench]

Do you have a PK for a Payment object? If not, what URL are you calling for this action?

[indigo belfry]

You can see it in a action function signature

[raw trench]

No I can't

[indigo belfry]

Sounds very strange because it oblivious

[raw trench]

I'm asking where you're getting the PK for that URL from

[indigo belfry]

Api/payments/pk/...

[indigo belfry]

You mean in view?

It's action, it implies having pk

[raw trench]

But you're taking that PK and expecting it to be a Borrowing object. It's attached to a Payment view set? So it's expected to be a Payment object.

[indigo belfry]

Got it...

[indigo belfry]

In this case how can I get borrowing object?

Not having pk ...

You mean just as related object?

Payment.borrowings.all()

But pk for borrowing is unreachable to me

[raw trench]

I don't understand what this endpoint is meant to do, and why it's on a Payment view set

If it's an action to apply to a Borrowing object then it should be on the Borrowing view set

[indigo belfry]

Well, saying pointfully

1. Endpoint is for purpose - to create new Stripe session because previous is expired

As payment process

2. If you run through all actions within PaymentViewSet you can see that all endpoints related to payment process is pulled in one viewset

Recreate session endpoint is related to payment process as well

[raw trench]

Then give it a payment PK, why do you need the Borrowing object?

[indigo belfry]

Well, but I need Borrowing object as well

[raw trench]

But isn't that just a FK from Payment?

It's very hard to reason about API endpoints when you don't know what's calling it or from what context

[indigo belfry]

Context is

To provide the entire payment process

1. Payment successful - url, on which customer will be redirected in case of successful payment

2. Payment cancel - endpoint on which customer will be redirected in case of payment failure

3. Recreate session url endpoint - endpoint on which customer will be redirected in case os payment session expires

It's oblivious Ben

[raw trench]

I think you mean "obvious", and it's obviously not obvious.

[indigo belfry]

Yes

[raw trench]

Customers shouldn't be redirected to API endpoints? I presume there's some JS going on here

[indigo belfry]

It's just mistake

[raw trench]

Does your front end know a primary key for the Payment object

[indigo belfry]

Yes

[raw trench]

Then use that.

[indigo belfry]

It's presumed

[raw trench]

Get the Payment object.

Get the borrowing object from the payment object.

[indigo belfry]

How get?

[raw trench]

Honestly with your designs we can't presume anything

[raw trench]

That's what self.get_object() does on a view set? Returns the object referenced by the URL

[indigo belfry]

You mixed up point

Get_object is related to Payment object

[raw trench]

Yes.

[indigo belfry]

Not to Borrowing

[raw trench]

Which I said.

Get the payment object.

Then get the borrowing object from the payment object.

they have a foreign key relationship

[indigo belfry]

Why we so long time discuss that oblivious thing?

I am just puzzled

[raw trench]

"obvious"

[indigo belfry]

Sorry, obvious

[indigo belfry]

Also, what is your consideration about in which view this action should be placed?

I mean - PaymentViewSet, BorrowingViewSet

[raw trench]

Well you told me it was obvious it should be in the payment view set 🤷‍♂️

[indigo belfry]

But occasionally you said it could be in Borrowing View Set

You have some pros to that?

[raw trench]

You were adamant you needed the Borrowing object, so it sounded like it was an action being applied to the Borrowing object 🤷‍♂️

[indigo belfry]

Ok, I see.

[indigo belfry]

Ok, thank you, Ben, a lot

I hope it will work out

[raw trench]

But all of this "where should it be" is just speculation without knowing the full data model design and how the front end uses it

[indigo belfry]

In nutshell it's library borrowing service?

There are books, you can borrow those and give back till expected return date

Also payment consists of 2 parts

1. Main part - payment for borrowing itself

2. Fine for overdue period

Payments are processed by Stripe gateway as the most effective payment handler

Comparing to other payments systems even PayPal and liqpay

Payment system is a peak of this project

The most difficult part

[indigo belfry]

Hello, Ben

Unfortunately I tried to get Payment object using both approaches.

And I want to say - neither using self.get_object(), nor using pk - didn't give results at all

Using both methods doesn't allow to get Payment object inside PaymentViewSet

Eventhough it must but for some reason doesn't

only approach which is really works as of now is using - Payment.objects.all()

and then just using this - queryset.first()