I am trying to use get_object to retrieve a single object from my database. However, my code always enters into get_queryset and not get_object so I always return a list of objects.
Here is my viewset :
class DiagramView(viewsets.ModelViewSet):
queryset = Diagram.objects.all()
serializer_class = DiagramSerializer
pk_url_kwarg = 'id'
def get_object(self, *args, **kwargs):
return self.queryset.get(id=kwargs.get('id'))
def get_queryset(self):
print('im here')
My route is :
router.register('api/diagramsingle', DiagramView, 'diagramsingle')
And I access this route like this :
api/diagramsingle/?id=1
Thank you for your answer.
As is written in the documentation on routers, for a SimpleRouter, the detail view has as pattern api/diagramsingle/<int:pk>/, so you access a single object with:
api/diagramsingle/1/
where you specify the primary key in the path, not in the querystring.
Related
i am having a tricky issue. In my views.py i am passing a form in a DetailView. But i am not using a FormMixin. That has the reason that i only want my template to render the form. In the template i use that form to trigger an UpdateView.
class UpdateDetailView(LoginRequiredMixin, DetailView):
model = Balance
def get_context_data(self, **kwargs):
context = super(UpdateDetailView, self).get_context_data(**kwargs)
context['form'] = ManagerForm
return context
def get_queryset(self, *args, **kwargs):
request = self.request
pk = self.kwargs.get('pk')
select = self.kwargs.get('select')
queryset = Balance.objects.filter(pk=pk).filter(owner = request.user).filter(select = select)
return queryset
class BalanceUpdateView(LoginRequiredMixin, UpdateView):
form_class = ManagerForm
model = Balance
def get_success_url(self):
return reverse('url-year', kwargs={'year': self.object.year, 'select': self.object.select})
So far, so good. The issue is that the form in the UpdateDetailView the ChoiceFields are showing select option of other users which one is not supposed to see. Thus i need to override the queryset of the Modelform. Usually i could use the get_form_kwargs method to pass the request.user to the form. But since the UpdateDetailView is not a FormView it doesnt have that (i know, coz i tried desperately). I also tried context['form'] = ManagerForm(initial = {'user': self.request.user}) in the get_context_data method. But i was unable to access user properly with the __init__ method in the forms.py. I got a key error. If i passed it as arg then i get an attribute error. Does anyone have a solution to that problem? Do i need to use a FormMixin?
Thank you for your replies!
What is the meaning of single model instance in RetrieveAPIView in Django REST framework.And how can we use? And will it look?
As my understanding:
single model instance: Example we use RetrieveAPIView. If we read the method that handle requests to that class, that is:
def retrieve(self, request, *args, **kwargs):
instance = self.get_object()
serializer = self.get_serializer(instance)
return Response(serializer.data)
We can see self.get_object(), it will build a Queryset to get object instance from our model class using method get(), or rather using get_object_or_404(). As we know, get() will only take 1 object instance, or it called single model instance.
Example Book.objects.get(id=10).
For more detail, we can open this link. Start from def retrieve then read also get_object().
Likewise on DestroyAPIView and UpdateAPIView.
collection of model instances: When build a Queryset, it using all() or filter(), according to what we wrote in queryset = .... or we override in def get_queryset. Example: Book.objects.all(). See this link and read def list.
CMIW.
I currently have the following serializer:
serializers.py
class SurfGroupSerializer(serializers.ModelSerializer):
instructor = SurfInstructorSerializer(many=False)
surfers = SurferSerializer(many=True)
class Meta:
model = SurfGroup
fields = ['uuid', 'instructor', 'date', 'starting_time', 'ending_time', 'surfers']
def create(self, validated_data):
return SurfGroup(**validated_data)
And the following viewset create method (viewset inherited from viewsets.ViewSet as we need some bespoke customization, extra signals and actions etc):
viewsets.py
# Surf Group Create View:
def create(self, request, format=None):
serializer = SurfGroupSerializer(data=request.data)
serializer.is_valid(raise_exception=True)
self.perform_create(serializer)
headers = self.get_success_headers(serializer.data)
response = responses.standardized_json_response(
message='Surf Group Objects Have Been Successfully Created',
data=serializer.data
)
return Response(data=response, status=status.HTTP_201_CREATED, headers=headers)
For the retrieve action, the serializer works well, and we have a nested instructor object in the response. However, I want to perform a create by passing in the instructor uuid attrbiute like (see content in the POST textarea):
Rather than a whole object...I was wondering how we achieve this? Is it best to just have two Serializers, one for performing the create, and one the retrieval?
def create(self, validated_data):
surf_group = SurfGroup(
instructor__uuid=validated_data['instructor'],
)
surf_group.save()
return surf_group
It is good question.
I work with this situations many times and it looks like one option is to have two serializers as you mean: 1 for list/retrieve and 1 for save.
Another option (for me) is to set serializer field input as UUID and output as another serializer data like this:
class SurfGroupSerializer(serializers.ModelSerializer):
instructor = serializers.UUIDField()
surfers = SurferSerializer(many=True, read_only=True)
class Meta:
model = SurfGroup
fields = ['uuid', 'instructor', 'date', 'starting_time', 'ending_time', 'surfers']
# I use this validate method to transform uuid to object which will
# be bypassed to create method for easly save
def validate_instructor(self, instructor_uuid):
try:
return Instructor.objects.get(uuid=instructor_uuid)
except Instructor.DoesNotExist:
# Remember that you dont need to pass field_key: [errors] to ValidationError
# because validate_FIELD will automatically pass field_key for you !
raise ValidationError(['Instructor with the given uuid does not exist.'])
# Overwrite output data
def to_representation(self, instance):
ret = super().to_representation(instance)
ret['instructor'] = SurfInstructorSerializer(instance=instance.instructor).data
return ret
I'm developing an API with Django Rest framework, and I would like to dynamically remove the fields from a serializer. The problem is that I need to remove them depending on the value of another field. How could I do that?
I have a serializer like:
class DynamicSerliazer(serializers.ModelSerializer):
type = serializers.SerializerMethodField()
url = serializers.SerializerMethodField()
title = serializers.SerializerMethodField()
elements = serializers.SerializerMethodField()
def __init__(self, *args, **kwargs):
super(DynamicSerliazer, self).__init__(*args, **kwargs)
if self.fields and is_mobile_platform(self.context.get('request', None)) and "url" in self.fields:
self.fields.pop("url")
As you can see, I'm already removing the field "url" depending whether the request has been done from a mobile platform. But, I would like to remove the "elements" field depending on the "type" value. How should I do that?
Thanks in advance
You can customize the serialization behavior by overriding the to_representation() method in your serializer.
class DynamicSerliazer(serializers.ModelSerializer):
def to_representation(self, obj):
# get the original representation
ret = super(DynamicSerializer, self).to_representation(obj)
# remove 'url' field if mobile request
if is_mobile_platform(self.context.get('request', None)):
ret.pop('url')
# here write the logic to check whether `elements` field is to be removed
# pop 'elements' from 'ret' if condition is True
# return the modified representation
return ret
You can create multiple serializers and choose the proper one in view
class IndexView(APIView):
def get_serializer_class(self):
if self.request.GET['flag']:
return SerializerA
return SerializerB
use inheritance to make serializers DRY.
My problem was somewhat similar to yours and I solved it with inheritance.
class StaticSerializer(serializers.ModelSerializer):
class Meta:
model = StaticModel
fields = (
'first_name', 'last_name', 'password', 'username',
'email'
)
class DynamicSerializer(StaticSerializer):
class Meta:
model = StaticModel
fields = (
'first_name',
)
Solution (ViewSet mixin)
I have solved this problem by writing my own ViewSet mixin. It provides quite easy and DRY way to override serializers depending on request action.
class ActionBasedSerializerClassMixin(viewsets.ModelViewSet):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
def get_serializer_class(self):
attr_name = f'{self.action}_serializer_class'
if hasattr(self, attr_name):
serializer_class = getattr(self, attr_name)
self.serializer_class = serializer_class
return super().get_serializer_class()
Usage
To use this mixin inherit from it at your viewset (It must be before ModelViewSet parent).
The default serializer is always used as fallback
To use different serializer on list action just set attribute list_serializer_class at your viewset:
class MyViewSet(ViewSet):
serializer_class = MySerializer
list_serializer_class = MyListSerializer
With this code you will have MyListSerializer when action is 'list' and MySerializer for all other actions.
The same patterns works for all other action types: list, create, retrieve, update, partial_update, destroy.
You just need to append _serializer_class to get desired attribute name.
How serailizers should look like
class MySerializer(serializers.ModelSerializer):
some_reverse_rel = MyOtherSerializer(many=True, read_only=True)
class Meta:
model = MyModel
fields = ['field1', 'field2', 'foo', 'bar', 'some_reverse_rel']
class MyListSerailizer(MySerializer): # Note that we inherit from previous serializer
some_reverse_rel = None # Getting rid of reverse relationship
class Meta(MySerializer.Meta):
fields = ['foo', 'bar', 'field1']
In order to have a non-readonly PrimaryKeyRelatedField, you are required to provide a queryset that contains valid options.
How can I properly populate that queryset based on the current request (user)?
The key is to subclass PrimaryKeyRelatedField and overload the get_queryset method, using the user information from the request context:
class UserFilteredPrimaryKeyRelatedField(serializers.PrimaryKeyRelatedField):
def get_queryset(self):
request = self.context.get('request', None)
queryset = super(UserFilteredPrimaryKeyRelatedField, self).get_queryset()
if not request or not queryset:
return None
return queryset.filter(user=request.user)
You can then use this new serializer just like the (unfiltered) original:
class MySerializer(serializers.ModelSerializer):
related = UserFilteredPrimaryKeyRelatedField(queryset=MyModel.objects)
Whenever the serializer accesses the queryset, it will be filtered such that only objects owned by the current user are returned.
View has a
self.request.user
attribute which you can then use to fetch user related queryset
eg
queryset = Products.objects.get(customer=self.request.user)