Right way to represent relationships links.related view?

[n2ygk]

I'm trying to correctly return a links.related view (not links.self) and haven't been able to find a good example. In looking at the example app it appears to have the same problem. Here's a fragment of my urlconf and view definitions:

router = routers.DefaultRouter()
router.register(r'courses', views.CourseViewSet)
router.register(r'course_terms', views.CourseTermViewSet)

urlpatterns = [
    url(r'^v1/', include(router.urls)),
    # http://127.0.0.1:8000/v1/courses/f009e671-b615-42c7-b35f-8500d7ef5d24/relationships/course_terms
    url(r'^v1/courses/(?P<pk>[^/.]+)/relationships/(?P<related_field>\w+)',
        views.CourseRelationshipView.as_view(),
        name='course-relationships'),
    # http://127.0.0.1:8000/v1/courses/f009e671-b615-42c7-b35f-8500d7ef5d24/course_terms/
    url(r'^v1/courses/(?P<fk>[^/.]+)/course_terms/',  # need fk (course_id) not pk (id)
        views.CourseTermViewSet.as_view({'get': 'list'}),
        name='course-course_terms'),
]

class CourseBaseViewSet(AuthnAuthzMixIn, SortMixin, FilterMixin, viewsets.ModelViewSet):
    pass


class CourseViewSet(CourseBaseViewSet):
    # API endpoint that allows course to be viewed or edited.
    queryset = Course.objects.all()
    serializer_class = CourseSerializer


class CourseTermViewSet(CourseBaseViewSet):
    # API endpoint that allows CourseTerm to be viewed or edited.
    queryset = CourseTerm.objects.all()
    serializer_class = CourseTermSerializer
#    queryset = queryset.filter(course_id='ec008c20-79a1-4ca7-931a-019d62c219c9')


class CourseRelationshipView(AuthnAuthzMixIn, RelationshipView):
    queryset = Course.objects
    self_link_view_name = 'course-relationships'

A get of a course looks like this:
GET http://127.0.0.1:8000/v1/courses/ec008c20-79a1-4ca7-931a-019d62c219c9/

{
    "data": {
        "type": "courses",
        "id": "ec008c20-79a1-4ca7-931a-019d62c219c9",
        "attributes": {
            "school_bulletin_prefix_code": "XCEFK9",
            "suffix_two": "00",
            "subject_area_code": "PSYB",
            "course_number": "00241",
            "course_identifier": "PSYC1138X",
            "course_name": "SOCIAL PSYCHOLOGY-LEC",
            "course_description": "SOCIAL PSYCHOLOGY-LEC",
            "effective_start_date": null,
            "effective_end_date": null,
            "last_mod_user_name": "loader",
            "last_mod_date": "2018-03-11"
        },
        "relationships": {
            "course_terms": {
                "data": [
                    {
                        "type": "course_terms",
                        "id": "3ce01e27-9a68-4970-b48a-e6a83166ca41"
                    }
                ],
                "links": {
                    "self": "http://127.0.0.1:8000/v1/courses/ec008c20-79a1-4ca7-931a-019d62c219c9/relationships/course_terms",
                    "related": "http://127.0.0.1:8000/v1/courses/ec008c20-79a1-4ca7-931a-019d62c219c9/course_terms/"
                },
                "meta": {
                    "count": 1
                }
            }
        },
        "links": {
            "self": "http://127.0.0.1:8000/v1/courses/ec008c20-79a1-4ca7-931a-019d62c219c9/"
        }
    }
}

But GET http://127.0.0.1:8000/v1/courses/ec008c20-79a1-4ca7-931a-019d62c219c9/course_terms/ returns all the course_terms, not just those with fk=ec008c20-79a1-4ca7-931a-019d62c219c9 because the foreign key is not being applied. (You can see where I tested and with queryset = queryset.filter(course_id='ec008c20-79a1-4ca7-931a-019d62c219c9')) so I'm wondering what the right way to do this is.

Am I missing something? I've reproduced this with the example app and it also does it "wrong". I think I need to extend the view function to check for some kwargs (e.g. fk) and filter the manager.

Thanks in advance for any help.

[n2ygk]

Here's my workaround but I suspect I'm just missing the obvious right way!
@sliverc -- Have you run into this?

1. revert the URLs back to pk:

    url(r'^v1/courses/(?P<pk>[^/.]+)/relationships/(?P<related_field>\w+)',
        views.CourseRelationshipView.as_view(),
        name='course-relationships'),
    url(r'^v1/courses/(?P<pk>[^/.]+)/course_terms/',
        views.CourseTermViewSet.as_view({'get': 'list'}),
        name='course-course_terms'),

2. extend list() to do the filtering when pk is present in kwargs.:

class CourseTermViewSet(CourseBaseViewSet):
    # API endpoint that allows CourseTerm to be viewed or edited.
    # if lookup_field (pk) is passed in to the view, then the query is filtered for matching foreign keys
    # TODO: there must be a correct way to do this as the RelationshipView does the right thing.
    queryset = CourseTerm.objects.all()
    serializer_class = CourseTermSerializer

    def list(self, request, *args, **kwargs):
        if __class__.lookup_field in kwargs:
            print("FK {}".format(kwargs[__class__.lookup_field]))
            self.queryset = self.get_queryset().filter(course_id=kwargs[__class__.lookup_field])
        return super(CourseTermViewSet, self).list(request, *args, **kwargs)

[sliverc]

I haven't really used RelationshipVIew. But I assume you have followed the documentation on http://django-rest-framework-json-api.readthedocs.io/en/stable/usage.html?highlight=RelationshipView#relationshipview

Potentially it is a bug. If you can reproduce it in the example app best write a test case and open a PR. Potentially a fix might be obvious then and can be added as well or someone else can have a look.

[n2ygk]

Yes, RelationShipView works fine in that it generates the appropriate related links.self and links.related URLs. There's just no documentation for how to correctly implement the view that corresponds to links.related and the example is incorrect in that it doesn't filter the child model by the parent's pk. I suspect it may not have been implemented. I'm thinking of reposting to stackoverflow as there's a larger audience there and maybe someone else has solved this already. Once I get a solution I'll submit a PR to fix the example and add more complete test cases.

…

On Fri, Apr 27, 2018 at 11:07 AM, Oliver Sauder ***@***.***> wrote: I haven't really used RelationshipVIew. But I assume you have followed the documentation on http://django-rest-framework- json-api.readthedocs.io/en/stable/usage.html?highlight=RelationshipView# relationshipview Potentially it is a bug. If you can reproduce it in the example app best write a test case and open a PR. Potentially a fix might be obvious then and can be added as well or someone else can have a look. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#426 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AEJ5d5yc3B3nlbmveX9H6xRDEdAo__rWks5tszQqgaJpZM4Tn0RK> .

[Anton-Shutik]

@n2ygk I think you can do like it was done in example:

Configure url with parameter named entry_pk. It is important to give another name then pk

url(r'entries/(?P<entry_pk>[^/.]+)/comments',
        CommentViewSet.as_view({'get': 'list'}),
        name='entry-comments'),

Then in the view you can check kwargs dict for that parameter, like this:

class CommentViewSet(ModelViewSet):
    ...

    def get_queryset(self, *args, **kwargs):
        entry_pk = self.kwargs.get('entry_pk', None)
        if entry_pk is not None:
            return self.queryset.filter(entry_id=entry_pk)

        return super(CommentViewSet, self).get_queryset()

Thus, it will return only comments related to given entry.

[n2ygk]

@Anton-Shutik Thanks, yes, here's what I've ended up with that works basically the same way, just overriding list:

router = rest_framework.routers.DefaultRouter()
# ...
router.register(r'course_terms', views.CourseTermViewSet)

urlpatterns = [
    # ...
    url(r'^v1/', include(router.urls)),
    url(r'^v1/course_terms/(?P<pk>[^/.]+)/relationships/(?P<related_field>\w+)',
        views.CourseTermRelationshipView.as_view(),
        name='course_term-relationships'),
    url(r'^v1/course_terms/(?P<pk>[^/.]+)/course/',
        views.CourseViewSet.as_view({'get': 'list'}),
        name='course_terms-course'),
]

class CourseTermViewSet(CourseBaseViewSet):
    queryset = CourseTerm.objects.all()
    serializer_class = CourseTermSerializer

    def list(self, request, *args, **kwargs):
        if __class__.lookup_field in kwargs:
            self.queryset = self.get_queryset().filter(course=kwargs[__class__.lookup_field])
        return super(CourseTermViewSet, self).list(request, *args, **kwargs)

What would be really nice to have is a router = rest_framework_json_api.routers.JSONAPIRouter()
that builds all the necessary URLs to implement the normal resource along with relationships and related URLs so that I can just router.register(r'course_terms') instead of having to explicitly create routes for relationships and related URLs and a rest_framework_json_api.views.ModelViewSet that extends list (my example) or get_queryset (your example).

[n2ygk]

@Anton-Shutik Maybe I should take a closer look at #451

[Anton-Shutik]

@n2ygk yep, probably @sliverc will merge it soon.