I am attempting to use drf-nested-routers to create a simple nested Django REST API given the following models:
# models.py
class Podcast(models.Model):
title = models.CharField(max_length=125)
class Episode(models.Model):
podcast = models.ForeignKey(Podcast, on_delete=models.CASCADE)
title = models.CharField(max_length=125)
Based on the readme domains/nameservers example, I have the following routers defined, expecting a URL structure like:
/podcasts[/{podcast_pk}[/episodes[/{episode_pk}]]]
# urls.py
router = routers.DefaultRouter()
router.register(r'podcasts', PodcastViewSet)
episode_router = routers.NestedDefaultRouter(
router, r'podcasts', lookup='podcast'
)
episode_router.register(
r'episodes', EpisodeViewSet, basename='podcast-episodes'
)
# serializers.py
class PodcastSerializer(HyperlinkedModelSerializer):
episodes = HyperlinkedIdentityField(
view_name='podcast-episodes-list',
lookup_url_kwarg='podcast_pk'
)
class Meta:
model = Podcast
fields = '__all__'
class EpisodeSerializer(NestedHyperlinkedModelSerializer):
parent_lookup_kwargs = {
'podcast_pk': 'podcast__pk',
}
class Meta:
model = Episode
fields = '__all__'
# exclude = ('url',) # works without reference to self
# views.py
class PodcastViewSet(viewsets.ModelViewSet):
queryset = Podcast.objects.all()
serializer_class = PodcastSerializer
class EpisodeViewSet(viewsets.ModelViewSet):
serializer_class = EpisodeSerializer
def get_queryset(self):
return Episode.objects.filter(
podcast=self.kwargs['podcast_pk'],
)
Accessing /podcasts/1/episodes/, when url is included, raises the following error:
Exception Type: ImproperlyConfigured at /podcasts/1/episodes/
Exception Value: Could not resolve URL for hyperlinked
relationship using view name "episode-detail". You may
have failed to include the related model in your API,
or incorrectly configured the `lookup_field` attribute
on this field.
Why does it not identify the correct view name, or is there something else obvious I am missing
In my case using 'id' instead of 'pk' is solved my problem.
parent_lookup_kwargs = {
'podcast_pk': 'podcast_id',
}
Related
We have a model with only one fields (Name). We want to send a list of dictionaries and create multiple objects for this model in one POST request. The model, serializer, view and mixin is mentioned below:
models.py
class Manufacturer(models.Model):
"""
The Measure Unit Category Table contains the categories
of measurement units (example: weight, length, temperature,etc)
"""
name = models.CharField(verbose_name=_("Manufacturer Name"),
help_text=_("Required. Example: Ford, Tesla, Hyundai"),
max_length=63,
unique=True)
class Meta:
verbose_name = _("Manufacturer")
verbose_name_plural = _("Manufacturers")
ordering = ('name',)
def __str__(self):
return self.name
serializers.py
class ManufacturerSerializer(serializers.ModelSerializer):
class Meta:
model = Manufacturer
fields = '__all__'
mixins.py
class CreateModelMixin(object):
def get_serializer(self, *args, **kwargs):
# add many=True if the data is of type list
if isinstance(kwargs.get("data", {}), list):
kwargs["many"] = True
return super().get_serializer(*args, **kwargs)
views.py
class ManufacturerCreateView(CreateModelMixin, generics.CreateAPIView):
"""
Create View for Manufacturer
"""
queryset = Manufacturer.objects.all()
serializer_class = ManufacturerSerializer
permission_classes = (IsAuthenticated,)
With the above code, I'm able to create multiple objects with one POST request.
I've written the below test case using pytest:
def test_create_manufacturer_list_of_objects(self, authenticated_client):
data = [
{
"name": "Test11"
},
{
"name": "Test12"
}
]
response = authenticated_client.post(reverse('manufacturer-create'), data)
assert response.status_code == 201
urls.py
path('create-manufacturer/',
ManufacturerCreateView.as_view(),
name='manufacturer-create'),
When I run the above, I get the error - AttributeError: 'list' object has no attribute 'items'.
This is a little confusing as the API works without any errors but the test case fails. Can you please guide on correcting this issue?
I tried overriding the POST method, and including the above code in serializers instead of mixins, but it gives the same error.
Passing the "format=json" when calling the post method resolved the issue.
Modified the test url to below:
response = authenticated_client.post(reverse('manufacturer-create'), data, format=json)
I want to use HyperLinkedModelSerializer in order to add a url field for my Book model. Here is the solution you'd typically find in the average tutorial:
# serializers.py
class BookSerializer(HyperLinkedModelSerializer):
class Meta:
model = Book
fields = ("title", "url",)
# views.py
class BookView(RetrieveAPIView):
serializer_class = BookSerializer
# urls.py
urlpatterns = [
path("<pk>/", BookDetailView.as_view(), name="book-detail"),
]
And that works all right. But now I need to change the URL conf in order to match the book id, not with <pk>, but with <fiction_id>. So I figured I'd just change it!
# urls.py
urlpatterns = [
path("<fiction_id>/", BookDetailView.as_view(), name="book-detail"),
]
Now comes the crash:
django.core.exceptions.ImproperlyConfigured: Could not resolve URL for hyperlinked relationship using view name "fiction-detail". You may have failed to include the related model in your API, or incorrectly configured the `lookup_field` attribute on this field.
I've tried fiddling with the lookup_field, lookup_url_kwargs in my view:
# views.py
class BookView(RetrieveAPIView):
serializer_class = BookSerializer
lookup_field = "pk"
lookup_url_kwargs = "fiction_id"
I've tried reminding the serializer to actually look for the (default) "pk":
# serializers.py
class BookSerializer(HyperLinkedModelSerializer):
class Meta:
model = Book
fields = ("title", "url",)
extra_kwargs = {
"url": {"lookup_field": "pk"},
}
I've tried combinations of these, to no avail. It looks like you can't use anything but <pk> if you want to take advantage of HyperLinkedModelSerializer's url field. The documentation doesn't seem to offer a way to change that behaviour:
By default hyperlinks are expected to correspond to a view name that matches the style '{model_name}-detail', and looks up the instance by a pk keyword argument.
How can I change this behaviour, or is it bound to become too messy?
You should check HyperlinkedModelSerializer implementation and see that it uses a serializer_related_field defaulting to HyperlinkedRelatedField
class HyperlinkedModelSerializer(ModelSerializer):
"""
A type of `ModelSerializer` that uses hyperlinked relationships instead
of primary key relationships. Specifically:
* A 'url' field is included instead of the 'id' field.
* Relationships to other instances are hyperlinks, instead of primary keys.
"""
serializer_related_field = HyperlinkedRelatedField
...
And then HyperlinkedRelatedField has a class attribute lookup_field defaulting to pk
class HyperlinkedRelatedField(RelatedField):
lookup_field = 'pk'
...
What you can do is to use a custom HyperlinkedRelatedField with your own lookup_field
from rest_framework.relations import HyperlinkedRelatedField
from rest_framework.serializers import HyperlinkedModelSerializer
class BookHyperlinkedRelatedField(HyperlinkedRelatedField):
lookup_field = 'fiction_id'
class BookSerializer(HyperLinkedModelSerializer):
serializer_related_field = BookHyperlinkedRelatedField
class Meta:
model = Book
fields = ("title", "url",)
In order to do this, you need to give the url field's new name for the lookup in the matched pattern by passing it through the extra_kwargs dictionary:
# serializers.py
class BookSerializer(HyperLinkedModelSerializer):
class Meta:
model = Book
fields = ("title", "url",)
extra_kwargs = {
"url": {"lookup_url_kwarg": "fiction_id"},
}
Also remember to modify the corresponding view:
# views.py
class BookView(RetrieveAPIView):
serializer_class = BookSerializer
lookup_url_kwarg = "fiction_id"
Do not write lookup_url_kwargs in plural.
You don't need to meddle with the lookup_field at any level as long as the lookup will be done on the model's primary key.
I have the following models:
class Contact(models.Model):
class Meta:
managed = False
db_table = 'contact'
class ContactPhone(models.Model):
contact = models.ForeignKey(Contact, on_delete = models.CASCADE)
number = models.CharField(max_length = 45)
class Meta:
managed = False
db_table = 'contact_phone'
Also, I have the following serializers:
class ContactSerializer(serializers.ModelSerializer):
server_id = serializers.IntegerField(source='id', read_only=True)
class Meta:
model = Contact
fields = '__all__'
class ContactPhoneSerializer(serializers.ModelSerializer):
class Meta:
model = ContactPhone
fields = '__all__'
Now, I have a view that insert phone numbers for an existing contact.
The input is a json that looks like this:
data = {'contact_id': 12322,
'phones':[{'number': '89120000001'}]}
The view:
def insert_contact_phone(request):
for record in request.data['phones']:
data['contact_id'] = request.data['contact_id']
serializer = ContactPhoneSerializer(data = data)
if serializer.is_valid():
serializer.save()
I end up with the following error:
RelatedObjectDoesNotExist at /contacts/edit ContactPhone has no
contact.
What am I doing wrong?
If you specify __all__ for the fields in your ContactPhoneSerializer, it does not include contact_id.
So the contact_id taken from the json input is not serialized. It is basically ignored and when you try to save and create new ContactPhone - it fails, because it does not have contact's foreign key correctly set.
But simply adding contact_id to the serializer's fields won't solve your problem.
In your view, i recommend you to set the contact instead:
data['contact'] = request.data['contact_id']
and pass this to the ContactPhoneSerializer.
How can I pass an argument to a serializers.RelatedField class from views.py. I need to pass language_id to query Language.objects model within that RelatedField.
I am not sure if I took a right approach to this issue. What I want to achieve is to present information about genres associated to a movie from database model about depending on the language. The MovieGenre model has genre ID field which I want to replace with actual Genre name.
My serialiser.py
class GenreField(serializers.RelatedField):
def to_representation(self, value, language_id=1):
genre_name = GenresVideo.objects.get(genre_id=value, language_id=language_id)
return genre_name.name
class MovieGenresSerializer(serializers.ModelSerializer):
genre_id = GenreField(read_only=True)
class Meta:
model = MoviesGenres
As you see, here I query Language.objects with default value but I would like to pass it from views (language_id).
My views.py:
class MovieGenresTestViewSet(viewsets.ModelViewSet):
lookup_field = 'movie'
queryset = MoviesGenres.objects.all()
serializer_class = MovieGenresSerializer
def list(self, request, language_pk):
queryset = MoviesGenres.objects.all()
serializer = MovieGenresSerializer(queryset, many=True)
return Response(serializer.data)
def retrieve(self, request, movie, language_pk):
queryset = MoviesGenres.objects.filter(movie=movie)
serializer = MovieGenresSerializer(queryset, many=True)
return Response(serializer.data)
And my urls.py:
router.register(r'lang', LanguagesViewSet, base_name='lang')
mov_gen = routers.NestedSimpleRouter(router, r'lang', lookup='language')
mov_gen.register(r'mg', MovieGenresTestViewSet, base_name='mg')
url(r'^api/', include(genre_spec.urls))
My models.py
class Languages(models.Model):
name = models.CharField(unique=True, max_length=255)
short_name = models.CharField(unique=True, max_length=4, blank=True, null=True)
active = models.BooleanField(default="")
class Meta:
managed = False
db_table = 'languages'
ordering = ('id',)
class GenresVideo(models.Model):
genre_id = models.IntegerField()
language = models.ForeignKey('Languages')
name = models.CharField(max_length=255, blank=True, null=True)
class Meta:
managed = False
db_table = 'genres_video'
unique_together = (('genre_id', 'language'),)
ordering = ('genre_id',)
class MoviesGenres(models.Model):
movie = models.ForeignKey(Movies)
genre_id = models.IntegerField()
class Meta:
managed = False
db_table = 'movies_genres'
unique_together = (('movie', 'genre_id'),)
Through the urls routes, I can get a correct response from API including the language_id. I just need to pass it to the view somehow.
Thanks a lot for help!
I'll try to answer to your first question, with the easiest implementation possible: SerializerMethodField. Because we will get the language id via the context passed to the serializer, we should either generate the context for the serializer, or let the framework do that for us.
Now to the problem at hand: you aren't filtering the queryset (MoviesGenres) by language per se. Thus, we can avoid overwriting the list and retrieve methods. Nevertheless, the router mechanism will inject in kwargs for the view method the language_pk parameter - that's the parameter that we will retrieve from within the serializer context:
class MovieGenresSerializer(serializers.ModelSerializer):
genre = searializers.SerializerMethodField()
class Meta:
model = MoviesGenres
def get_genre(self, instance):
# get the language id from the view kwargs
language_id = self.context['view'].kwargs['language_pk']
# get the genre
try:
genre_name = GenresVideo.objects.get(genre_id=instance.genre_id, language_id=language_id).name
except GenresVideo.DoesNotExist:
genre_name = None
# return the formatted output
return genre_name
class MovieGenresTestViewSet(viewsets.ModelViewSet):
lookup_field = 'movie'
queryset = MoviesGenres.objects.all()
serializer_class = MovieGenresSerializer
I think this is simple and probably a duplicate, but I cannot figure it out by looking at the documentation.
I have Django models as follows:
class Image(models.Model):
manor = models.ForeignKey(Manor, related_name='image_for_manor')
filename = models.CharField(max_length=30, null=True, blank=True)
class Manor(models.Model):
id = models.IntegerField(primary_key=True)
I want the user to be able to query the Manor and see the related Image. I'd like this JSON to be returned:
{
id: 572,
image: 'my/filepath.png'
}
This is my view:
#api_view(['GET'])
def manor(request, id):
mymanor = Manor.objects.get(id=id)
serializer = ManorSerializer(mymanor)
return JSONResponse(serializer.data)
And these are my serializers:
class ImageFilePathSerializer(serializers.ModelSerializer):
class Meta:
model = Image
fields = ('filename',)
class ManorSerializer(serializers.ModelSerializer):
image = ImageFilePathSerializer(source="image_for_manor")
class Meta:
model = Manor
fields = ('id', 'image')
But this doesn't work: I get an empty dictionary for image. (Even if it weren't empty, I realise it wouldn't be right, because I don't want the image property to be a dictionary: I want it to be a string.)
How can I change this to be correct? I cannot work it out.
As Kevin suggested , why dont you use ImageField which will give you url where your image is uploaded. although if you dont want to do that , here are some changes you have to do to get the result format you wanted.(Following solution assumes that only one image will be for one minor)
views.py ( why dont you ImageFilePathSerializer instead of another one as it also contains all the data you wanted)
#api_view(['GET'])
def manor(request, id):
mymanor = Image.objects.get(manor__id=id)
serializer = ImageFilePathSerializer(mymanor)
return Response(serializer.data)
serializers.py (add Id with filename in ImageFilePathSerializer)
class ImageFilePathSerializer(serializers.ModelSerializer):
class Meta:
model = Image
fields = ('id', 'filename',)
class ManorSerializer(serializers.ModelSerializer):
filename = serializers.ImageField(source="image_for_manor")
class Meta:
model = Manor
fields = ('id', 'filename')