I have a route that uses a ViewSet
router.register(
r'mapping_details',
GlobalMappingDetailsViewSet,
base_name='global-store-product-mappings'
)
This view set contains a get_queryset method and a serializer.
class GlobalMappingDetailsViewSet(viewsets.ModelViewSet):
serializer_class = GlobalMappingDetailsSerializer
def get_queryset(self):
return models.Mappings.objects.all().select_related('my_column')
class GlobalMappingDetailsSerializer(serializers.ModelSerializer):
class Meta:
model = models.Mappings
fields = ('column1', 'column2')
I want to add 2 fields that are populated using a single API call in the response of the request. I could use serializers.Field but will have to make separate calls for both the fields.
Does someone know the right way to handle this use case?
The way to do this is by overriding the Django Viewset actions. In my case I needed to just populate the response in the fields, I overrode the list and retrieve actions and added the fields to the response.
Some sample code:
def retrieve(self, request, *args, **kwargs):
response = super(GlobalMappingDetailsViewSet, self).retrieve(request, *args, **kwargs)
data = response.data
api_response = MyService.make_api_call(data.get('id'))
data['my_new_field'] = api_response.get('response_field', '')
return response
I'm working on my Django SAAS app in which I want to allow the user to have some custom settings, like disable or enable certain filters. For that I'm using django-user-setttings combined with django-filters and simple forms with boolean fields:
class PropertyFilterSetting(forms.Form):
filter_by_loans = forms.BooleanField(required=False)
filter_by_tenants = forms.BooleanField(required=False)
The issue is that when trying to apply those settings, I keep running into serious spaghetti code:
views.py
class PropertyListView(LoginRequiredMixin, FilterView):
template_name = 'app/property_list.html'
context_object_name = 'properties'
def get_filterset_class(self):
print(get_user_setting('filter_by_tenants', request=self.request))
return PropertyFilterWithoutTenant if not get_user_setting('filter_by_tenants', request=self.request)['value'] else PropertyFilter
filter.py
class PropertyFilter(django_filter.FilterSet):
...
class PropertyFilterWithoutTenant(PropertyFilter):
...
and I'd have to do the same thing with the rest of the features. Is there any better way to implement this?
You can create methods in your User model, or a new class which acts as a store for all the methods. Each method will give you the relevant filterset class based on the value of corresponding user setting.
Something like:
class UserFilterset:
def __init__(self, request):
self.request = request
def get_property_filterset(self):
if not get_user_setting('filter_by_tenants', request=self.request)['value']:
return PropertyFilterWithoutTenant
return PropertyFilter
... # add more such methods for each user setting
Now you can use this method to get the relevant filterset class
class PropertyListView(LoginRequiredMixin, FilterView):
template_name = 'app/property_list.html'
context_object_name = 'properties'
def get_filterset_class(self):
return UserFilterset(self.request).get_property_filterset()
So even if in future you want to add some more logic, you can just update the relevant method, it would be cleaner and manageable.
I'm not sure how MVT stucture will exactly respond to this one but i use a custom generic class in REST structure to add custom filter fields in any viewset that i want
class ListAPIViewWithFilter(ListAPIView):
def get_kwargs_for_filtering(self):
filtering_kwargs = {}
if self.my_filter_fields is not []:
# iterate over the filter fields
for field in self.my_filter_fields:
# get the value of a field from request query parameter
field_value = self.request.query_params.get(field)
if field_value:
filtering_kwargs[field] = field_value
return filtering_kwargs
def get_queryset(self):
queryset = super(ListAPIViewWithFilter, self).get_queryset()
filtering_kwargs = self.get_kwargs_for_filtering()
if filtering_kwargs != {}:
# filter the queryset based on 'filtering_kwargs'
queryset = queryset.filter(**filtering_kwargs)
self.pagination_class = None
else:
return queryset
return queryset[:self.filter_results_number_limit]
changing origional get_queryset function in views.py should be the key to solving your problem (it works in django rest).
try checking what function gets the data then just identify the field wanted from it.
What i currently have setted up with django rest is :
MODEL NAME : Animes
/api/ <- root
/api/animes/ <- lists all animes available in my db
/api/animes/id/ <- returns the anime instance that has id=id
MODEL NAME : Episodes
/api/ <- root
/api/episodes/ <- lists all episodes of all animes available in my db
/api/episodes/id/ <- returns the episode instance that has id=id
So basically im trying to achieve is :
if i request api/episodes/{anime_name}/
i get that specific anime's Episodes listed .
how can i do that ?
EpisodesSerializer
class EpisodesSerializer(serializers.ModelSerializer):
class Meta:
model = Episodes
fields = '__all__'
Router
router = routers.DefaultRouter()
router.register('animes', AnimesViewSet, 'animes')
router.register('episodes', EpisodesViewSet, 'episodes')
urlpatterns = router.urls
EpisodesViewSet
class EpisodesViewSet(viewsets.ModelViewSet):
permission_classes = [permissions.AllowAny]
MainModel = Episodes
queryset = Episodes.objects.all()
serializer_class = EpisodesSerializer
EDIT
As the OP mentioned in the comments, the newer versions of DRF use #action instead as #detail_route and #list_route are deprecated.
To use a different field for lookup, you can implement the logic to get the object yourself but you have to make sure that the field you're using for lookup is unique, else you can have many objects returned.
So assuming the anime name is unique and you want to use it for lookup, you can do this:
#action(detail=True, methods=['get'])
def episodes(self, *args, **kwargs):
anime = Anime.objects.get(name=self.kwarg[self.lookup_field])
episodes = Episode.objects.filter(anime=anime)
...
You can also check how get_object() is implemented to make it more robust.
I made a generic view mixin for myself that allows lookup with multiple unique fields aprt from the main pk lookup field:
class AlternateLookupFieldsMixin(object):
"""
Looks up objects for detail endpoints using alternate
lookup fields assigned in `alternate_lookup_fields` apart
from the default lookup_field. Only unique fields should be used
else Http404 is raised if multiple objects are found
"""
alternate_lookup_fields = []
def get_object(self):
try:
return super().get_object()
except Http404:
lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field
queryset = self.filter_queryset(self.get_queryset())
obj = None
for lookup_field in self.alternate_lookup_fields:
filter_kwargs = {lookup_field: self.kwargs[lookup_url_kwarg]}
try:
obj = get_object_or_404(queryset, **filter_kwargs)
except Http404:
pass
if obj:
self.check_object_permissions(self.request, obj)
return obj
raise Http404
All you have to do is add it to your view's base classes and add the fields for lookup(name in your case) in the alternate_lookup_fields attribute. Of course, only use unique fields.
As for filtering, you can check how simple filtering is done here.
However, I will recommend using a more generic filter backend like django-filter
ORIGINAL ANSWER
First of all, the url will look more initutive like this:
api/anime/<anime_id>/episodes/
This is because you should usually start from a more generic resource to more specific ones.
To achieve this, in your AnimeViewSet(not EpisodesViewSet), you can have a detail route for the episodes like this:
from rest_framework.decorators import detail_route
#detail_route(methods=['get'])
def episodes(self, *args, **kwargs):
anime = self.get_object()
episodes = Episode.objects.filter(anime=anime)
page = self.paginate_queryset(anime)
if page is not None:
serialier = EpisodesSerializer(page, context=self.get_serializer_context(), many=True)
return self.get_paginated_response(serializer.data)
serializer = EpisodesSerializer(episodes, context=self.get_serializer_context()) many=True)
return Response(serializer.data)
You could also just use a filter on the EpisodesViewSet to fetch episodes belonging to a particular anime this way:
api/episodes?anime=<anime_id>
I'm trying to implement partial_update with Django Rest Framework but I need some clarification because I'm stuck.
Why do we need to specify partial=True?
In my understanding, we could easily update Demo object inside of partial_update method. What is the purpose of this?
What is inside of serialized variable?
What is inside of serialized variable in partial_update method? Is that a Demo object? What function is called behind the scenes?
How would one finish the implementation here?
Viewset
class DemoViewSet(viewsets.ModelViewSet):
serializer_class = DemoSerializer
def partial_update(self, request, pk=None):
serialized = DemoSerializer(request.user, data=request.data, partial=True)
return Response(status=status.HTTP_202_ACCEPTED)
Serializer
class DemoSerializer(serializers.ModelSerializer):
class Meta:
model = Demo
fields = '__all__'
def update(self, instance, validated_data):
print 'this - here'
demo = Demo.objects.get(pk=instance.id)
Demo.objects.filter(pk=instance.id)\
.update(**validated_data)
return demo
I when digging into the source code of rest_framework and got the following findings:
For question 1. Why do we need to specify partial=True?
This question is related to HTTP verbs.
PUT: The PUT method replaces all current representations of the target resource with the request payload.
PATCH: The PATCH method is used to apply partial modifications to a resource.
Generally speaking, partial is used to check whether the fields in the model is needed to do field validation when client submitting data to the view.
For example, we have a Book model like this, pls note both of the name and author_name fields are mandatory (not null & not blank).
class Book(models.Model):
name = models.CharField('name of the book', max_length=100)
author_name = models.CharField('the name of the author', max_length=50)
# Create a new instance for testing
Book.objects.create(name='Python in a nut shell', author_name='Alex Martelli')
For some scenarios, we may only need to update part of the fields in the model, e.g., we only need to update name field in the Book. So for this case, client will only submit the name field with new value to the view. The data submit from the client may look like this:
{"pk": 1, name: "PYTHON IN A NUT SHELL"}
But you may have notice that our model definition does not allow author_name to be blank. So we have to use partial_update instead of update. So the rest framework will not perform field validation check for the fields which is missing in the request data.
For testing purpose, you can create two views for both update and partial_update, and you will get more understanding what I just said.
Example:
views.py
from rest_framework.generics import GenericAPIView
from rest_framework.mixins import UpdateModelMixin
from rest_framework.viewsets import ModelViewSet
from rest_framework import serializers
class BookSerializer(serializers.ModelSerializer):
class Meta:
model = Book
class BookUpdateView(GenericAPIView, UpdateModelMixin):
'''
Book update API, need to submit both `name` and `author_name` fields
At the same time, or django will prevent to do update for field missing
'''
queryset = Book.objects.all()
serializer_class = BookSerializer
def put(self, request, *args, **kwargs):
return self.update(request, *args, **kwargs)
class BookPartialUpdateView(GenericAPIView, UpdateModelMixin):
'''
You just need to provide the field which is to be modified.
'''
queryset = Book.objects.all()
serializer_class = BookSerializer
def put(self, request, *args, **kwargs):
return self.partial_update(request, *args, **kwargs)
urls.py
urlpatterns = patterns('',
url(r'^book/update/(?P<pk>\d+)/$', BookUpdateView.as_view(), name='book_update'),
url(r'^book/update-partial/(?P<pk>\d+)/$', BookPartialUpdateView.as_view(), name='book_partial_update'),
)
Data to submit
{"pk": 1, name: "PYTHON IN A NUT SHELL"}
When you submit the above json to the /book/update/1/, you will got the following error with HTTP_STATUS_CODE=400:
{
"author_name": [
"This field is required."
]
}
But when you submit the above json to /book/update-partial/1/, you will got HTTP_STATUS_CODE=200 with following response,
{
"id": 1,
"name": "PYTHON IN A NUT SHELL",
"author_name": "Alex Martelli"
}
For question 2. What is inside of serialized variable?
serialized is a object wrapping the model instance as a serialisable object. and you can use this serialized to generate a plain JSON string with serialized.data .
For question 3. How would one finish the implementation here?
I think you can answer yourself when you have read the answer above, and you should have known when to use update and when to used partial_update.
If you still have any question, feel free to ask. I just read part of the source code of the rest framework, and may have not understand very deeply for some terms, and please point it out when it is wrong...
For partial update - PATCH http method
For full update - PUT http method
When doing an update with DRF, you are supposed to send request data that includes values for all (required) fields. This is at least the case when the request is via the PUT http method. From what I understand, you want to update one or at least not all model instance fields. In this case make a request with the PATCH http method. Django rest framework (DRF) will take care of it out of the box.
Example (with token auth):
curl -i -X PATCH -d '{"name":"my favorite banana"}' -H "Content-Type: application/json" -H 'Authorization: Token <some token>' http://localhost:8000/bananas/
So simple, just override init method of your serializer like that:
def __init__(self, *args, **kwargs):
kwargs['partial'] = True
super(DemoSerializer, self).__init__(*args, **kwargs)
Just a quick note as it seems that nobody has already pointed this out:
serialized = DemoSerializer(request.user, data=request.data, partial=True)
The first argument of DemoSerializer should be a Demo instance, not a user (at least if you use DRF 3.6.2 like me).
I don't know what you are trying to do, but this is a working example:
def partial_update(self, request, *args, **kwargs):
response_with_updated_instance = super(DemoViewSet, self).partial_update(request, *args, **kwargs)
Demo.objects.my_func(request.user, self.get_object())
return response_with_updated_instance
I do the partial update and then I do other things calling my_func and passing the current user and the demo instance already updated.
Hope this helps.
I had an issue where my multi-attribute/field validation in a rest_framework serializer was working with a POST /resources/ request but failing with a PATCH /resources/ request. It failed in the PATCH case because it was only looking for values in the supplied attrs dict and not falling back to values in self.instance. Adding a method get_attr_or_default to do that fallback seems to have worked:
class EmailSerializer(serializers.ModelSerializer):
def get_attr_or_default(self, attr, attrs, default=''):
"""Return the value of key ``attr`` in the dict ``attrs``; if that is
not present, return the value of the attribute ``attr`` in
``self.instance``; otherwise return ``default``.
"""
return attrs.get(attr, getattr(self.instance, attr, ''))
def validate(self, attrs):
"""Ensure that either a) there is a body or b) there is a valid template
reference and template context.
"""
existing_body = self.get_attr_or_default('body', attrs).strip()
if existing_body:
return attrs
template = self.get_attr_or_default('template', attrs)
templatecontext = self.get_attr_or_default('templatecontext', attrs)
if template and templatecontext:
try:
render_template(template.data, templatecontext)
return attrs
except TemplateRendererException as err:
raise serializers.ValidationError(str(err))
raise serializers.ValidationError(NO_BODY_OR_TEMPLATE_ERROR_MSG)
I don't know why, but for me, the only way to solve it was to override the validate method in the Serializer class.
Maybe it's related to the fact that I'm using MongoDB with Djongo
class DemoSerializer(serializers.ModelSerializer):
def validate(self, attrs):
self._kwargs["partial"] = True
return super().validate(attrs)
You forgot serializer.save()
You can finish it the following way . . .
class DemoViewSet(viewsets.ModelViewSet):
serializer_class = DemoSerializer
def partial_update(self, request, pk=None):
serializer = DemoSerializer(request.user, data=request.data, partial=True)
serializer.save()
serializer.is_valid(raise_exception=True)
return Response(serializer.data)
Also, you shouldn't need to override the update method in the serializer.
Hi there I want to create a custom method in a modelviewset which needs to perform a save and an update logic in a single post request.
Here is my breeding.viewsets.py
class BreedingViewSet(viewsets.ModelViewSet):
queryset = Breeding.objects.all()
serializer_class = BreedingSerializer
Since the above method has a higher level of abstraction and is
actually providing or performing automatic CRUD functions.
Now the problem here is i dont have any control for a multiple queries like saving an object and updating another object in a single post request.
e.g
def save_and_update(self, request):
// do save an object here.
// do update an object here.
How can we achieve such powerful functionalities? Did i missed something? I found this documentation but i dont know how to implement the given instruction.
UPDATE
This is what im looking for How do I create multiple model instances with Django Rest Framework?
But the answer can only save a multiple instances in a single post request of that same model. But Im hoping also that we can perform queries for a different models in that single function.
Well, from the comments, it looks like you want to update some unrelated model when you create your breeding model. This should be easy.
class BreedingViewSet(viewsets.ModelViewSet):
queryset = Breeding.objects.all()
serializer_class = BreedingSerializer
def create(self, request):
# do your thing here
return super().create(request)
Use this to create or update using POST
class BreedingViewSet(viewsets.ModelViewSet):
queryset = Breeding.objects.all()
serializer_class = BreedingSerializer
def get_object(self):
if self.action == 'create':
queryset = self.filter_queryset(self.get_queryset())
filter_kwargs = {self.lookup_field: self.request.data.get('id')}
obj = get_object(queryset, **filter_kwargs)
self.check_object_permissions(self.request, obj)
return obj
else:
return super(BreedingViewSet, self).get_object()
def create(self, request, *args, **kwargs):
if request.data.get('id'):
return super(BreedingViewSet, self).update(request, *args, **kwargs)
else:
return super(BreedingViewSet, self).create(request, *args, **kwargs)