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Django REST Framework how to add context to a ViewSet

The ViewSets do everything that I want, but I am finding that if I want to pass extra context to a template (with TemplateHTMLRenderer) then I will have to get at the functions that give responses.. (like list(), create(), etc)
The only way I can see to get into these is to completely redefine them in my ViewSet, but it seems that there should be an easy way to add a bit of context to the Template without having to redefine a whole set of methods...
class LanguageViewSet(viewsets.ModelViewSet):
"""Viewset for Language objects, use the proper HTTP methods to modify them"""
# TODO: add permissions for this view?
queryset = Language.objects.all()
serializer_class = LanguageSerializer
filter_backends = (filters.DjangoFilterBackend, )
filter_fields = ('name', 'active')
Right now my code is looking like this but I will be wanting to add different context to the responses and I am trying to avoid redefining an entire method for such a small change. like this...
class LanguageViewSet(viewsets.ModelViewSet):
"""Viewset for Language objects, use the proper HTTP methods to modify them"""
# TODO: add permissions for this view?
queryset = Language.objects.all()
serializer_class = LanguageSerializer
filter_backends = (filters.DjangoFilterBackend, )
filter_fields = ('name', 'active')
def list(self, **kwargs):
"""Redefinition of list"""
..blah blah everything that list does
return Response({"foo": "bar"}, template_name="index.html")

I faced the same issue and resolved in a slightly different way in Django Rest Framework (DRF) 3.x. I believe it is not necessary to override the relatively complex render method on the TemplateHTMLRenderer class, but only the much simpler method get_template_context (or: resolve_context in earlier versions of DRF).
The procedure is as follows:
Override the get_renderer_context method on your ViewSet (as already suggested):
def get_renderer_context(self):
context = super().get_renderer_context()
context['foo'] = 'bar'
return context
Subclass TemplateHTMLRenderer, but only override the get_template_context method instead of the entire render method (render calls self.get_template_context to retrieve the final context to pass to the template):
class ModifiedTemplateHTMLRenderer(TemplateHTMLRenderer):
def get_template_context(self, data, renderer_context):
"""
Override of TemplateHTMLRenderer class method to display
extra context in the template, which is otherwise omitted.
"""
response = renderer_context['response']
if response.exception:
data['status_code'] = response.status_code
return data
else:
context = data
# pop keys which we do not need in the template
keys_to_delete = ['request', 'response', 'args', 'kwargs']
for item in keys_to_delete:
renderer_context.pop(item)
for key, value in renderer_context.items():
if key not in context:
context[key] = value
return context
{{ foo }} is now available as a template variable - as are all other variables added in get_renderer_context.

Although I disagree with 'pleasedontbelong' in principle, I agree with him on the fact that the extra contextual data ought to be emitted from the serializer. That seems to be the cleanest way since the serializer would be returning a native python data type which all renderers would know how to render.
Heres how it would look like:
ViewSet:
class LanguageViewSet(viewsets.ModelViewSet):
queryset = Language.objects.all()
serializer_class = LanguageSerializer
filter_backends = (filters.DjangoFilterBackend, )
filter_fields = ('name', 'active')
def get_serializer_context(self):
context = super().get_serializer_context()
context['foo'] = 'bar'
return context
Serializer:
class YourSerializer(serializers.Serializer):
field = serializers.CharField()
def to_representation(self, instance):
ret = super().to_representation(instance)
# Access self.context here to add contextual data into ret
ret['foo'] = self.context['foo']
return ret
Now, foo should be available inside your template.
Another way to achieve this, in case you don't wish to mess with your serializers, would be to create a custom TemplateHTMLRenderer.
class TemplateHTMLRendererWithContext(TemplateHTMLRenderer):
def render(self, data, accepted_media_type=None, renderer_context=None):
# We can't really call super in this case, since we need to modify the inner working a bit
renderer_context = renderer_context or {}
view = renderer_context.pop('view')
request = renderer_context.pop('request')
response = renderer_context.pop('response')
view_kwargs = renderer_context.pop('kwargs')
view_args = renderer_context.pop('args')
if response.exception:
template = self.get_exception_template(response)
else:
template_names = self.get_template_names(response, view)
template = self.resolve_template(template_names)
context = self.resolve_context(data, request, response, render_context)
return template_render(template, context, request=request)
def resolve_context(self, data, request, response, render_context):
if response.exception:
data['status_code'] = response.status_code
data.update(render_context)
return data
To add data into the context, ViewSets provide a get_renderer_context method.
class LanguageViewSet(viewsets.ModelViewSet):
queryset = Language.objects.all()
serializer_class = LanguageSerializer
filter_backends = (filters.DjangoFilterBackend, )
filter_fields = ('name', 'active')
def get_renderer_context(self):
context = super().get_renderer_context()
context['foo'] = 'bar'
return context
{'foo': 'bar'} should now be available in your template.

Django REST specify which fields when viewing a list

By default, when asking a list of a model like "/cars", django rest outputs all of the model data. I want it to output only pk's on a list request, and full model data on a detail request. I am using ModelSerializer and ModelViewSet.
PS. Is it supposed to be like this by design? Pulling so much unneeded data seems like such a waste.
Thanks :)

You can simply override the 'list' method of viewset to get desired response like this:
from rest_framework.response import Response
def list(self, request, *args, **kwargs):
pks = []
qs = self.get_queryset()
for obj in qs:
pks.append(obj.pk)
return Response(data=pks)

I customized the code to suit my requirement. I created the following 2 mixins. Make your APIListView extend FieldFilterMixin and your serializer extend SerializerFieldsMixin. Pass fl in GET request with comma separated values to get the required fields in response.
class SerializerFieldsMixin(object):
"""
Return only the fields asked for.
Don't return any extra fields in serializer.
"""
def get_fields(self):
all_fields = super(SerializerFieldsMixin,self).get_fields()
asked_fields = self.context.get('asked_fields')
if not asked_fields:
return all_fields
all_fields = OrderedDict([(k,v) for k,v in all_fields.items() if k in asked_fields])
return all_fields
class FieldFilterMixin(object):
"""
To be used with List/Retrieve views.
Set class attribute fields for the fields you want to display.
Or override get_required_fields to customize.
"""
def get_required_fields(self):
if self.request.GET.has_key("fl"):
return self.request.GET["fl"]
return []
def get_serializer_context(self):
methods_to_act_on = ["GET","HEAD"]
context = super(FieldFilterMixin,self).get_serializer_context()
asked_fields = self.get_required_fields()
if asked_fields and self.request.method in methods_to_act_on:
context["asked_fields"] = asked_fields
return context

Dynamically exclude or include a field in Django REST framework serializer

I have a serializer in Django REST framework defined as follows:
class QuestionSerializer(serializers.Serializer):
id = serializers.CharField()
question_text = QuestionTextSerializer()
topic = TopicSerializer()
Now I have two API views that use the above serializer:
class QuestionWithTopicView(generics.RetrieveAPIView):
# I wish to include all three fields - id, question_text
# and topic in this API.
serializer_class = QuestionSerializer
class QuestionWithoutTopicView(generics.RetrieveAPIView):
# I want to exclude topic in this API.
serializer_class = ExamHistorySerializer
One solution is to write two different serializers. But there must be a easier solution to conditionally exclude a field from a given serializer.

Have you tried this technique
class QuestionSerializer(serializers.Serializer):
def __init__(self, *args, **kwargs):
remove_fields = kwargs.pop('remove_fields', None)
super(QuestionSerializer, self).__init__(*args, **kwargs)
if remove_fields:
# for multiple fields in a list
for field_name in remove_fields:
self.fields.pop(field_name)
class QuestionWithoutTopicView(generics.RetrieveAPIView):
serializer_class = QuestionSerializer(remove_fields=['field_to_remove1' 'field_to_remove2'])
If not, once try it.

Creating a new serializer is the way to go. By conditionally removing fields in a serializer you are adding extra complexity and making you code harder to quickly diagnose. You should try to avoid mixing the responsibilities of a single class.
Following basic object oriented design principles is the way to go.
QuestionWithTopicView is a QuestionWithoutTopicView but with an additional field.
class QuestionSerializer(serializers.Serializer):
id = serializers.CharField()
question_text = QuestionTextSerializer()
topic = TopicSerializer()
class TopicQuestionSerializer(QuestionSerializer):
topic = TopicSerializer()

You can set fields and exclude properties of Meta
Here is an Example:
class DynamicFieldsModelSerializer(serializers.ModelSerializer):
class Meta:
model = User
exclude = ['id', 'email', 'mobile']
def __init__(self, *args, **kwargs):
super(DynamicFieldsModelSerializer, self).__init__(*args, **kwargs)
# #note: For example based on user, we will send different fields
if self.context['request'].user == self.instance.user:
# Or set self.Meta.fields = ['first_name', 'last_name', 'email', 'mobile',]
self.Meta.exclude = ['id']

Extending above answer to a more generic one
class QuestionSerializer(serializers.Serializer):
def __init__(self, *args, **kwargs):
fields = kwargs.pop('fields', None)
super(QuestionSerializer, self).__init__(*args, **kwargs)
if fields is not None:
allowed = set(fields.split(','))
existing = set(self.fields)
for field_name in existing - allowed:
self.fields.pop(field_name)
class QuestionWithoutTopicView(generics.RetrieveAPIView):
def get_serializer(self, *args, **kwargs):
kwargs['context'] = self.get_serializer_context()
fields = self.request.GET.get('display')
serializer_class = self.get_serializer_class()
return serializer_class(fields=fields,*args, **kwargs)
def get_serializer_class(self):
return QuestionSerializer
Now we can give a query parameter called display to output any custom display format http://localhost:8000/questions?display=param1,param2

You can use to representation method and just pop values:
def to_representation(self, instance):
"""Convert `username` to lowercase."""
ret = super().to_representation(instance)
ret.pop('username') = ret['username'].lower()
return ret
you can find them here
https://www.django-rest-framework.org/api-guide/serializers/#overriding-serialization-and-deserialization-behavior

Pass extra arguments to Serializer Class in Django Rest Framework

I want to pass some arguments to DRF Serializer class from Viewset, so for I have tried this:
class OneZeroSerializer(rest_serializer.ModelSerializer):
def __init__(self, *args, **kwargs):
print args # show values that passed
location = rest_serializer.SerializerMethodField('get_alternate_name')
def get_alternate_name(self, obj):
return ''
class Meta:
model = OneZero
fields = ('id', 'location')
Views
class OneZeroViewSet(viewsets.ModelViewSet):
serializer_class = OneZeroSerializer(realpart=1)
#serializer_class = OneZeroSerializer
queryset = OneZero.objects.all()
Basically I want to pass some value based on querystring from views to Serializer class and then these will be allocate to fields.
These fields are not include in Model in fact dynamically created fields.
Same case in this question stackoverflow, but I cannot understand the answer.
Can anyone help me in this case or suggest me better options.

It's very easy with "context" arg for "ModelSerializer" constructor.
For example:
in view:
my_objects = MyModelSerializer(
input_collection,
many=True,
context={'user_id': request.user.id}
).data
in serializers:
class MyModelSerializer(serializers.ModelSerializer):
...
is_my_object = serializers.SerializerMethodField('_is_my_find')
...
def _is_my_find(self, obj):
user_id = self.context.get("user_id")
if user_id:
return user_id in obj.my_objects.values_list("user_id", flat=True)
return False
...
so you can use "self.context" for getting extra params.
Reference

You could in the YourView override get_serializer_context method like that:
class YourView(GenericAPIView):
def get_serializer_context(self):
context = super().get_serializer_context()
context["customer_id"] = self.kwargs['customer_id']
context["query_params"] = self.request.query_params
return context
or like that:
class YourView(GenericAPIView):
def post(self, request, *args, **kwargs):
serializer = self.get_serializer(data=request.data)
serializer.context["customer_id"] = request.user.id
serializer.context["query_params"] = request.query_params
serializer.is_valid(raise_exception=True)
...
and anywhere in your serializer you can get it. For example in a custom method:
class YourSerializer(ModelSerializer):
def get_alternate_name(self, obj):
customer_id = self.context["customer_id"]
query_params = self.context["query_params"]
...

To fulfill the answer of redcyb - consider using in your view the get_serializer_context method from GenericAPIView, like this:
def get_serializer_context(self):
return {'user': self.request.user.email}

A old code I wrote, that might be helpful- done to filter nested serializer:
class MySerializer(serializers.ModelSerializer):
field3 = serializers.SerializerMethodField('get_filtered_data')
def get_filtered_data(self, obj):
param_value = self.context['request'].QUERY_PARAMS.get('Param_name', None)
if param_value is not None:
try:
data = Other_model.objects.get(pk_field=obj, filter_field=param_value)
except:
return None
serializer = OtherSerializer(data)
return serializer.data
else:
print "Error stuff"
class Meta:
model = Model_name
fields = ('filed1', 'field2', 'field3')
How to override get_serializer_class:
class ViewName(generics.ListAPIView):
def get_serializer_class(self):
param_value = self.context['request'].QUERY_PARAMS.get('Param_name', None)
if param_value is not None:
return Serializer1
else:
return Serializer2
def get_queryset(self):
.....
Hope this helps people looking for this.

List of element if your query is a list of elements:
my_data = DataSerializers(queryset_to_investigate,
many=True, context={'value_to_pass': value_passed}
in case off single data query:
my_data = DataSerializers(queryset_to_investigate,
context={'value_to_pass': value_passed}
Then in the serializers:
class MySerializer(serializers.ModelSerializer):
class Meta:
fields = '__all__'
model = 'Name_of_your_model'
def on_representation(self, value):
serialized_data = super(MySerializer, self).to_representation(value)
value_as_passed = self.context['value_to_pass']
# ..... do all you need ......
return serialized_data
As you can see printing the self inside on_representation you can see: query_set: <object (x)>, context={'value_to_pass': value_passed}
This is a simpler way, and you can do this in any function of serializers having self in the parameter list.

These answers are far to complicated; If you have any sort of authentication then add this property to your serializer and call it to access the user sending the request.
class BaseSerializer(serializers.ModelSerializer):
#property
def sent_from_user(self):
return self.context['request'].user

Getting the context kwargs passed to a serializer like;
...
self.fields['category'] = HouseCategorySerializer(read_only=True, context={"all_fields": False})
...
In your serializer, that is HouseCategorySerializer do this in one of your functions
def get_houses(self, instance):
print(self._context.get('all_fields'))
Using self._context.get('keyword') solved my mess quickly, instead of using self.get_extra_context()

Add user specific fields to Django REST Framework serializer

I want to add a field to a serializer that contains information specific to the user making the current request (I don't want to create a separate endpoint for this). Here is the way I did it:
The viewset:
class ArticleViewSet(viewsets.ModelViewSet):
queryset = Article.objects.all()
serializer_class = ArticleSerializer
filter_class = ArticleFilterSet
def prefetch_likes(self, ids):
self.current_user_likes = dict([(like.article_id, like.pk) for like in Like.objects.filter(user=self.request.user, article_id__in=ids)])
def get_object(self, queryset=None):
article = super(ArticleViewSet, self).get_object(queryset)
self.prefetch_likes([article.pk])
return article
def paginate_queryset(self, queryset, page_size=None):
page = super(ArticleViewSet, self).paginate_queryset(queryset, page_size)
if page is None:
return None
ids = [article.pk for article in page.object_list]
self.prefetch_likes(ids)
return page
The serializer:
class ArticleSerializer(serializers.ModelSerializer):
class Meta:
model = Article
def to_native(self, obj):
ret = super(ArticleSerializer, self).to_native(obj)
if obj:
view = self.context['view']
ret['has_liked'] = False
if hasattr(view, 'current_user_liked'):
ret['has_liked'] = obj.pk in view.current_user_liked
return ret
Is there a better place to inject the prefetching of liked articles, or a nicer way to do this in general?

you can do it with SerializerMethodField
Example :
class PostSerializer(serializers.ModelSerializer):
fav = serializers.SerializerMethodField('likedByUser')
def likedByUser(self, obj):
request = self.context.get('request', None)
if request is not None:
try:
liked=Favorite.objects.filter(user=request.user, post=obj.id).count()
return liked == 1
except Favorite.DoesNotExist:
return False
return "error"
class Meta:
model = Post
then you should call serializer from view like this:
class PostView(APIVIEW):
def get(self,request):
serializers = PostSerializer(PostObjects,context={'request':request})

I'd be inclined to try and put as much of this as possible on the Like model object and then bung the rest in a custom serializer field.
In serializer fields you can access the request via the context parameter that they inherit from their parent serializer.
So you might do something like this:
class LikedByUserField(Field):
def to_native(self, article):
request = self.context.get('request', None)
return Like.user_likes_article(request.user, article)
The user_likes_article class method could then encapsulate your prefetching (and caching) logic.
I hope that helps.

According to the Django Documentation - SerializerMethodField, I had to change the code of rapid2share slightly.
class ResourceSerializer(serializers.ModelSerializer):
liked_by_user = serializers.SerializerMethodField()
def get_liked_by_user(self, obj : Resource):
request = self.context.get('request')
return request is not None and obj.likes.filter(user=request.user).exists()