I want to create a dynamic form field that always filters a model and shows the filtered elements in a list in the form. Here is the code I have so far:
class OrganisorClassStatusUpdateForm(forms.ModelForm):
def __init__(self, *args, **kwargs):
super(OrganisorClassStatusUpdateForm, self).__init__(*args, **kwargs)
self.fields['off_day_student'] = forms.ModelChoiceField(
queryset=Class.objects.filter(teacher=self.object.teacher).filter(is_new_set=True).filter(time=self.object.time).order_by('-date')[:10]
)
The problem I have with this code is that the self.object refers to the form itself, not the model I am trying to update. This is important since I need to filter the queryset using some of the information in the model I am trying to update. Please ask me any question if you need anything. Thanks a lot.
I need to pass id from the url slug. I am using generic views. This is my code for urls.py:
path('category/<int:pk>/details/',
CategoryDetailView.as_view(),
name='category-details'),
and I need to pass the <int:pk> value into views.py, so I can filter my queryset with this id.
My views.py code:
class CategoryDetailView(DetailView):
model = Category
def get_context_data(self, *, object_list=Expense.objects.get_queryset(), **kwargs):
queryset = object_list
return super().get_context_data(
summary_per_year_month = summary_per_year_month(queryset.filter(category_id= <int:pk> ))
)
You can access values from the URL in self.kwargs.
queryset.filter(category_id=self.kwargs['pk'])
Note that your get_context_data is the other way round than normal. Typically, you call super() and then add to the context dict. It looks like your way will work, but it will seem odd to other Django users. You could try writing it as follows:
def get_context_data(self, **kwargs):
context = super().get_context_data(**kwargs)
queryset=Expense.objects.get_queryset()
context['summary_per_year_month'] = summary_per_year_month(queryset.filter(category_id=self.kwargs['pk']))
return context
Yes, the path parameters are stored in self.kwargs, a dictionary that maps the name of the parameter to the value. So you can make use of:
class CategoryDetailView(DetailView):
model = Category
def get_context_data(self, *args, **kwargs):
summary=summary_per_year_month(
Expense.objects.filter(category_id=self.kwargs['pk'])
)
return super().get_queryset(*args, **kwargs, summary_per_year_month=summary)
You use self.kwargs.get('pk').
class CategoryDetailView(DetailView):
model = Category
def get_context_data(self, *, object_list=Expense.objects.get_queryset(), **kwargs):
queryset = object_list
return super().get_context_data(
summary_per_year_month = summary_per_year_month(queryset.filter(category_id=self.kwargs.get('pk')))
)
Something that really helped me learn Django was to add breakpoints (pdb) in my code, then run dir() on each object I came across.
For example, dir(self) will tell you what properties and methods 'self' has (ie, kwargs, model, request, etc). Then you can start experimenting around with these properties: self.kwargs, self.request, self.model, etc, see what they return.
Soon enough, you would find out that self.kwargs returns a dictionary of arguments that includes 'pk', which you can access using get(). That's how you can access 'pk'.
To me, this simple trick unlocked most of my understanding of Django and python.
i am working on a django project and struggling to understand class based views.
class readBooks(TemplateView):
template_name="books_read.html"
def get_context_data(self, **kwargs):
context = super(readBooks, self).get_context_data(**kwargs)
return context
def get_books(self):
wb=books.objects.all()
return wb
This is my class.
Problem is using get_books function is not callable.how am i goin to call this function.
sorry if i being too stupid asking. But i could not think of a better place than this.
I also need to understand how am i goin to use the returned result of this function in the Html file.
I am very new to django and Django tutorial is not so helpful for me.Any help is highly appreciated.
You should use generic model interface of Class-Based Views
# Use this snippet to call Books.objects.all()
class ReadBooks(ListView):
template_name = "books_read.html"
model = Books
# if you want filter the Book model
class ReadBooks(ListView):
template_name = "books_read.html"
model = Books
def get_queryset(self, *args, **kwargs):
return self.model.objects.filter(author='someone')
that's the beauty of the Class-Based Views, if you just need the all records of books, the code below is enough but ig you want to more customization for the view like calling other model queries, then you should use get_context_data
class ReadBooks(ListView):
template_name = "books_read.html"
model = Books
def get_context_data(self, *args, **kwargs):
ctx = super(ReadBooks, self).get_context_data(*args, **kwargs)
ctx['authors'] = Author.objects.all()
return ctx
Using Django REST Framework, I want to limit which values can be used in a related field in a creation.
For example consider this example (based on the filtering example on https://web.archive.org/web/20140515203013/http://www.django-rest-framework.org/api-guide/filtering.html, but changed to ListCreateAPIView):
class PurchaseList(generics.ListCreateAPIView)
model = Purchase
serializer_class = PurchaseSerializer
def get_queryset(self):
user = self.request.user
return Purchase.objects.filter(purchaser=user)
In this example, how do I ensure that on creation the purchaser may only be equal to self.request.user, and that this is the only value populated in the dropdown in the form in the browsable API renderer?
I ended up doing something similar to what Khamaileon suggested here. Basically I modified my serializer to peek into the request, which kind of smells wrong, but it gets the job done... Here's how it looks (examplified with the purchase-example):
class PurchaseSerializer(serializers.HyperlinkedModelSerializer):
def get_fields(self, *args, **kwargs):
fields = super(PurchaseSerializer, self).get_fields(*args, **kwargs)
fields['purchaser'].queryset = permitted_objects(self.context['view'].request.user, fields['purchaser'].queryset)
return fields
class Meta:
model = Purchase
permitted_objects is a function which takes a user and a query, and returns a filtered query which only contains objects that the user has permission to link to. This seems to work both for validation and for the browsable API dropdown fields.
Here's how I do it:
class PurchaseList(viewsets.ModelViewSet):
...
def get_serializer(self, *args, **kwargs):
serializer_class = self.get_serializer_class()
context = self.get_serializer_context()
return serializer_class(*args, request_user=self.request.user, context=context, **kwargs)
class PurchaseSerializer(serializers.ModelSerializer):
...
def __init__(self, *args, request_user=None, **kwargs):
super(PurchaseSerializer, self).__init__(*args, **kwargs)
self.fields['user'].queryset = User._default_manager.filter(pk=request_user.pk)
The example link does not seem to be available anymore, but by reading other comments, I assume that you are trying to filter the user relationship to purchases.
If i am correct, then i can say that there is now an official way to do this. Tested with django rest framework 3.10.1.
class UserPKField(serializers.PrimaryKeyRelatedField):
def get_queryset(self):
user = self.context['request'].user
queryset = User.objects.filter(...)
return queryset
class PurchaseSeriaizer(serializers.ModelSerializer):
users = UserPKField(many=True)
class Meta:
model = Purchase
fields = ('id', 'users')
This works as well with the browsable API.
Sources:
https://github.com/encode/django-rest-framework/issues/1985#issuecomment-328366412
https://medium.com/django-rest-framework/limit-related-data-choices-with-django-rest-framework-c54e96f5815e
I disliked the style of having to override the init method for every place where I need to have access to user data or the instance at runtime to limit the queryset. So I opted for this solution.
Here is the code inline.
from rest_framework import serializers
class LimitQuerySetSerializerFieldMixin:
"""
Serializer mixin with a special `get_queryset()` method that lets you pass
a callable for the queryset kwarg. This enables you to limit the queryset
based on data or context available on the serializer at runtime.
"""
def get_queryset(self):
"""
Return the queryset for a related field. If the queryset is a callable,
it will be called with one argument which is the field instance, and
should return a queryset or model manager.
"""
# noinspection PyUnresolvedReferences
queryset = self.queryset
if hasattr(queryset, '__call__'):
queryset = queryset(self)
if isinstance(queryset, (QuerySet, Manager)):
# Ensure queryset is re-evaluated whenever used.
# Note that actually a `Manager` class may also be used as the
# queryset argument. This occurs on ModelSerializer fields,
# as it allows us to generate a more expressive 'repr' output
# for the field.
# Eg: 'MyRelationship(queryset=ExampleModel.objects.all())'
queryset = queryset.all()
return queryset
class DynamicQuersetPrimaryKeyRelatedField(LimitQuerySetSerializerFieldMixin, serializers.PrimaryKeyRelatedField):
"""Evaluates callable queryset at runtime."""
pass
class MyModelSerializer(serializers.ModelSerializer):
"""
MyModel serializer with a primary key related field to 'MyRelatedModel'.
"""
def get_my_limited_queryset(self):
root = self.root
if root.instance is None:
return MyRelatedModel.objects.none()
return root.instance.related_set.all()
my_related_model = DynamicQuersetPrimaryKeyRelatedField(queryset=get_my_limited_queryset)
class Meta:
model = MyModel
The only drawback with this is that you would need to explicitly set the related serializer field instead of using the automatic field discovery provided by ModelSerializer. i would however expect something like this to be in rest_framework by default.
In django rest framework 3.0 the get_fields method was removed. But in a similar way you can do this in the init function of the serializer:
class PurchaseSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Purchase
def __init__(self, *args, **kwargs):
super(PurchaseSerializer, self).__init__(*args, **kwargs)
if 'request' in self.context:
self.fields['purchaser'].queryset = permitted_objects(self.context['view'].request.user, fields['purchaser'].queryset)
I added the if check since if you use PurchaseSerializer as field in another serializer on get methods, the request will not be passed to the context.
First to make sure you only allow "self.request.user" when you have an incoming http POST/PUT (this assumes the property on your serializer and model is named "user" literally)
def validate_user(self, attrs, source):
posted_user = attrs.get(source, None)
if posted_user:
raise serializers.ValidationError("invalid post data")
else:
user = self.context['request']._request.user
if not user:
raise serializers.ValidationError("invalid post data")
attrs[source] = user
return attrs
By adding the above to your model serializer you ensure that ONLY the request.user is inserted into your database.
2) -about your filter above (filter purchaser=user) I would actually recommend using a custom global filter (to ensure this is filtered globally). I do something for a software as a service app of my own and it helps to ensure each http request is filtered down (including an http 404 when someone tries to lookup a "object" they don't have access to see in the first place)
I recently patched this in the master branch so both list and singular views will filter this
https://github.com/tomchristie/django-rest-framework/commit/1a8f07def8094a1e34a656d83fc7bdba0efff184
3) - about the api renderer - are you having your customers use this directly? if not I would say avoid it. If you need this it might be possible to add a custom serlializer that would help to limit the input on the front-end
Upon request # gabn88, as you may know by now, with DRF 3.0 and above, there is no easy solution.
Even IF you do manage to figure out a solution, it won't be pretty and will most likely fail on subsequent versions of DRF as it will override a bunch of DRF source which will have changed by then.
I forget the exact implementation I used, but the idea is to create 2 fields on the serializer, one your normal serializer field (lets say PrimaryKeyRelatedField etc...), and another field a serializer method field, which the results will be swapped under certain cases (such as based on the request, the request user, or whatever). This would be done on the serializers constructor (ie: init)
Your serializer method field will return a custom query that you want.
You will pop and/or swap these fields results, so that the results of your serializer method field will be assigned to the normal/default serializer field (PrimaryKeyRelatedField etc...) accordingly. That way you always deal with that one key (your default field) while the other key remains transparent within your application.
Along with this info, all you really need is to modify this: http://www.django-rest-framework.org/api-guide/serializers/#dynamically-modifying-fields
I wrote a custom CustomQueryHyperlinkedRelatedField class to generalize this behavior:
class CustomQueryHyperlinkedRelatedField(serializers.HyperlinkedRelatedField):
def __init__(self, view_name=None, **kwargs):
self.custom_query = kwargs.pop('custom_query', None)
super(CustomQueryHyperlinkedRelatedField, self).__init__(view_name, **kwargs)
def get_queryset(self):
if self.custom_query and callable(self.custom_query):
qry = self.custom_query()(self)
else:
qry = super(CustomQueryHyperlinkedRelatedField, self).get_queryset()
return qry
#property
def choices(self):
qry = self.get_queryset()
return OrderedDict([
(
six.text_type(self.to_representation(item)),
six.text_type(item)
)
for item in qry
])
Usage:
class MySerializer(serializers.HyperlinkedModelSerializer):
....
somefield = CustomQueryHyperlinkedRelatedField(view_name='someview-detail',
queryset=SomeModel.objects.none(),
custom_query=lambda: MySerializer.some_custom_query)
#staticmethod
def some_custom_query(field):
return SomeModel.objects.filter(somefield=field.context['request'].user.email)
...
I did the following:
class MyModelSerializer(serializers.ModelSerializer):
myForeignKeyFieldName = MyForeignModel.objects.all()
def get_fields(self, *args, **kwargs):
fields = super(MyModelSerializer, self).get_fields()
qs = MyModel.objects.filter(room=self.instance.id)
fields['myForeignKeyFieldName'].queryset = qs
return fields
I looked for a solution where I can set the queryset upon creation of the field and don't have to add a separate field class. This is what I came up with:
class PurchaseSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Purchase
fields = ["purchaser"]
def get_purchaser_queryset(self):
user = self.context["request"].user
return Purchase.objects.filter(purchaser=user)
def get_extra_kwargs(self):
kwargs = super().get_extra_kwargs()
kwargs["purchaser"] = {"queryset": self.get_purchaser_queryset()}
return kwargs
The main issue for tracking suggestions regarding this seems to be drf#1985.
Here's a re-usable generic serializer field that can be used instead of defining a custom field for every use case.
class DynamicPrimaryKeyRelatedField(serializers.PrimaryKeyRelatedField):
"""A PrimaryKeyRelatedField with ability to set queryset at runtime.
Pass a function in the `queryset_fn` kwarg. It will be passed the serializer `context`.
The function should return a queryset.
"""
def __init__(self, queryset_fn=None, **kwargs):
assert queryset_fn is not None, "The `queryset_fn` argument is required."
self.queryset_fn = queryset_fn
super().__init__(**kwargs)
def get_queryset(self):
return self.queryset_fn(context=self.context)
Usage:
class MySerializer(serializers.ModelSerializer):
my_models = DynamicPrimaryKeyRelatedField(
queryset_fn=lambda context: MyModel.objects.visible_to_user(context["request"].user)
)
# ...
Same works for serializers.SlugRelatedField.
I have the following ModelForm:
class AttendanceForm(forms.ModelForm):
def __init__(self, *args, **kwargs):
operation_id = kwargs['operation_id']
del kwargs['operation_id']
super(AttendanceForm, self).__init__(*args, **kwargs)
self.fields['deployment'].query_set = \
Deployment.objects.filter(operation__id=operation_id)
class Meta:
model = Attendance
When I manually create the form in the shell (using manage.py shell)
form = AttendanceForm(operation_id=1)
form.fields['deployment'].query_set
it returns the correct query_set, but when I call
form.as_p()
i get extra entries that weren't in the query_set? Does django cache the html output somehow? I looked through the source, but couldn't find any caching. What am I doing wrong?
The parameter is queryset, not query_set. See the documentation.