I've been scratching my head about this problem for a couple of hours now. Basically, I have two models: User and Project:
class User(AbstractUser):
username = None
email = models.EmailField("Email Address", unique=True)
avatar = models.ImageField(upload_to="avatars", default="avatars/no_avatar.png")
first_name = models.CharField("First name", max_length=50)
last_name = models.CharField("Last name", max_length=50)
objects = UserManager()
USERNAME_FIELD = "email"
class Project(models.Model):
name = models.CharField("Name", max_length=8, unique=True)
status = models.CharField(
"Status",
max_length=1,
choices=[("O", "Open"), ("C", "Closed")],
default="O",
)
description = models.CharField("Description", max_length=3000, default="")
owner = models.ForeignKey(
User, on_delete=models.SET_NULL, null=True, related_name="project_owner"
)
participants = models.ManyToManyField(User, related_name="project_participants", blank=True)
created_at = models.DateTimeField(auto_now_add=True)
I use standard ModelViewSets for both of them, nothing changed. Then there's my Project serializer:
class ProjectSerializer(serializers.ModelSerializer):
class Meta:
model = Project
fields = "__all__"
status = serializers.CharField(source="get_status_display", required=False)
owner = UserSerializer()
participants = UserSerializer(many=True)
I use UserSerializers here, because having them achieved first of my two goals:
I wanted to get the user data when getting the project from the API -> owner is a serialized User with all the fields, same for participants, but it's a list of users
I want to be able to partially update the Project, for example add a participant
So I searched through the docs and SO and I always found answers that answer one of those questions, but never both of them.
The thing with my second goal is: when I do the partial update (via PATCH, of course), I get the response that: "Invalid data. Expected a dictionary, but got int." when I pass a list of ints (user ids) for the participants. I thought: okay, maybe I have to pass the whole user data to change it. But then I realised: when I remove the UserSerializer from ProjectSerializer - passing just the list of ints in Postman works just fine. And that is a life saver, cuz who wants to create a request with a whole bunch of data, when I can just pass user ids.
But then of course when I remove the UserSerializer, when I call get project, I get participants: [1,2,3,4,...], not participants: [{"id": 1, "name": "John", ...}, ...}]. And I really want this behavior, because I don't want to make additional API calls just to get the users' data by their IDs.
So summing up my question is: Is there a way to leave those serializers in place but still be able to partially update my model without having to pass whole serialized data to the API (dicts instead of IDs)? Frankly, I don't care about the serializers, so maybe the question is this: Can I somehow make it possible to partially update my Products' related fields like owner or participants just by passing the related entities IDs while still maintaining an ability to get my projects with those fields expanded (serialized entities - dicts, instead of just IDs)?
#Edit:
My view:
from rest_framework import viewsets, permissions
from projects.models import Project
from projects.api.serializers import ProjectSerializer
class ProjectViewSet(viewsets.ModelViewSet):
queryset = Project.objects.all()
serializer_class = ProjectSerializer
permission_classes = [permissions.IsAuthenticated]
lookup_field = "name"
def get_queryset(self):
if self.request.user.is_superuser:
return Project.objects.all()
else:
return Project.objects.filter(owner=self.request.user.id)
def perform_create(self, serializer):
serializer.save(owner=self.request.user, participants=[self.request.user])
Answer:
To anyone reading this, I've solved this problem and I actually created a base class for all my viewsets that I want this behavior to be in:
from rest_framework.response import Response
class ReadWriteViewset:
write_serializer_class = None
read_serializer_class = None
def update(self, request, *args, **kwargs):
partial = kwargs.pop("partial", False)
instance = self.get_object()
write_serializer = self.write_serializer_class(
instance=instance,
data=request.data,
partial=partial,
)
write_serializer.is_valid(raise_exception=True)
self.perform_update(write_serializer)
read_serializer = self.read_serializer_class(instance)
if getattr(instance, "_prefetched_objects_cache", None):
# If 'prefetch_related' has been applied to a queryset, we need to
# forcibly invalidate the prefetch cache on the instance.
instance._prefetched_objects_cache = {}
return Response(read_serializer.data)
Then you use it kinda like in here
I'm assuming that you are using a ModelViewSet. You could use different serializers for different methods.
class ProjectViewSet(viewsets.ModelViewSet):
def get_serializer_class(self):
if self.action in ['create', 'update']:
return WriteProjectSerializer # your serializer not using `UserSerializer` that works for updating
return ProjectSerializer # your default serializer with all data
Edit for using different serializers in same method:
# you can override `update` and use a different serializer in the response. The rest of the code is basically the default behavior
def update(self, request, *args, **kwargs):
partial = kwargs.pop('partial', False)
instance = self.get_object()
write_serializer = WriteProjectSerializer(data=request.data)
serializer.is_valid(raise_exception=True)
instance = self.perform_update(serializer)
read_serializer = ProjectSerializer(instance)
if getattr(instance, '_prefetched_objects_cache', None):
# If 'prefetch_related' has been applied to a queryset, we need to
# forcibly invalidate the prefetch cache on the instance.
instance._prefetched_objects_cache = {}
return Response(read_serializer.data)
A good way to see the default code for all these methods is using Classy DRF. You can see all methods that come with using ModelViewSet and use that code with some changes. Here I'm using the default code for update but changing for a new serializer for the response.
Related
SOLUTION AT THE BOTTOM
Problem: Django form populating with list of objects rather than values
Summary: I have 2 models Entities and Breaks. Breaks has a FK relationship to the entity_id (not the PK) on the Entities model.
I want to generate an empty form for all the fields of Breaks. Generating a basic form populates all the empty fields, but for the FK it generates a dropdown list of all objects of the Entities table. This is not helpful so I have excluded this in the ModelForm below and tried to replace with a list of all the entity_ids of the Entities table. This form renders as expected.
class BreakForm(ModelForm):
class Meta:
model = Breaks
#fields = '__all__'
exclude = ('entity',)
def __init__(self, *args, **kwargs):
super(BreakForm, self).__init__(*args, **kwargs)
self.fields['entity_id'] = ModelChoiceField(queryset=Entities.objects.all().values_list('entity_id', flat=True))
The below FormView is the cbv called by the URL. As the below stands if I populate the form, and for the FK column entity_id choose one of the values, the form will not submit. By that field on the form template the following message appears Select a valid choice. That choice is not one of the available choices.
class ContactFormView(FormView):
template_name = "breaks/test/breaks_form.html"
form_class = BreakForm
My initial thoughts were either that the datatype of this field (string/integer) was wrong or that Django needed the PK of the row in the Entities table (for whatever reason).
So I added a post function to the FormView and could see that the request.body was populating correctly. However I can't work out how to populate this into the ModelForm and save to the database, or overcome the issue mentioned above.
Addendum:
Models added below:
class Entity(models.Model):
pk_securities = models.AutoField(primary_key=True)
entity_id = models.CharField(unique=True)
entity_description = models.CharField(blank=True, null=True)
class Meta:
managed = False
db_table = 'entities'
class Breaks(models.Model):
pk_break = models.AutoField(primary_key=True)
date = models.DateField(blank=True, null=True)
entity = models.ForeignKey(Entity, on_delete= models.CASCADE, to_field='entity_id')
commentary = models.CharField(blank=True, null=True)
active = models.BooleanField()
def get_absolute_url(self):
return reverse(
"item-update", args=[str(self.pk_break)]
)
def __str__(self):
return f"{self.pk_break}"
class Meta:
managed = False
db_table = 'breaks'
SOLUTION
Firstly I got this working by adding the following to the Entity Model class. However I didn't like this as it would have consequences elsewhere.
def __str__(self):
return f"{self.entity_id}"
I found this SO thread on the topic. The accepted answer is fantastic and the comments to it are helpful.
The solution is to subclass ModelChoiceField and override the label_from_instance
class EntityChoiceField(ModelChoiceField):
def label_from_instance(self, obj):
return obj.entity_id
I think your problem is two fold, first is not rendering the dropdown correctly and second is form is not saving. For first problem, you do not need to do any changes in ModelChoiceField queryset, instead, add to_field_name:
class BreakForm(ModelForm):
class Meta:
model = Breaks
#fields = '__all__'
def __init__(self, *args, **kwargs):
super(BreakForm, self).__init__(*args, **kwargs)
self.fields['entity_id'] = ModelChoiceField(queryset=Entities.objects.all(), to_field_name='entity_id')
Secondly, if you want to save the form, instead of FormView, use CreateView:
class ContactFormView(CreateView):
template_name = "breaks/test/breaks_form.html"
form_class = BreakForm
model = Breaks
In Django, the request object passed as parameter to your view has an attribute called "method" where the type of the request is set, and all data passed via POST can be accessed via the request. POST dictionary. The view will display the result of the login form posted through the loggedin. html.
I might not get understand the concept of serializers right but as I think, serializers are used to represent python objects as json objects.
So my question is, I've got a model:
class User(AbstractUser):
messages = models.IntegerField(default=0)
signup_date = models.DateField(auto_now_add=True)
last_msg = models.DateField(null=True, blank=True)
and a serializer:
class UserSerializer(serializers.ModelSerializer):
password = serializers.CharField(write_only=True)
class Meta:
model = User
fields = ['username', 'password', 'email']
As my API View returns json, I want to pass a serialized username but I don't know how to achieve it.
This is a piece of code written without serializers so I'm trying to get the same result using them:
chat_session = ChatSession.objects.get(uri=uri)
owner = chat_session.owner
if owner != user: # Only allow non owners join the room
chat_session.members.get_or_create(
user=user, chat_session=chat_session
)
owner = deserialize_user(owner)
members = [
deserialize_user(chat_session.user)
for chat_session in chat_session.members.all()
]
How can I access my Serializer for a specific user instead of using a custom deserialize_user function
I believe
members = UserSerializer(many=True).to_representation(chat_session.members.all())
would do the trick.
I have two models first as parent model "Country", that filled before the second one as child model "City". as the following
class Country(models.Model):
name = models.CharField(max_length=35)
icon = models.ImageField()
def __str__(self):
return self.name
class City(models.Model):
name = models.CharField(max_length=35)
country = models.ForeignKey(to=Country, on_delete=models.CASCADE)
def __str__(self):
return self.name
My serializers.py for my need as following :
class CountrySerializer(ModelSerializer):
class Meta:
model = Country
fields = '__all__'
class CitySerializer(ModelSerializer):
country = serializers.PrimaryKeyRelatedField(queryset=Country.objects.all())
class Meta:
model = City
fields = ('name', 'country')
view.py
class CountryAPIView(ListAPIView):
queryset = Country.objects.all()
serializer_class = CountrySerializer
permission_classes = [AllowAny, AllowAnonymous]
class CityAPIView(ListAPIView):
queryset = City.objects.all()
serializer_class = CitySerializer
permission_classes = [AllowAny, AllowAnonymous]
def post(self, request):
serializer = CitySerializer(data=request.data)
if serializer.is_valid(raise_exception=ValueError):
serializer.create(validated_data=request.data)
return Response(serializer.data, status=status.HTTP_201_CREATED)
return Response(serializer.error_messages,
status=status.HTTP_400_BAD_REQUEST)
now when i run get api it run and gives me a result fine . But when im trying to create a new city and set "country":"id" in json i got this error
Cannot assign "2": "City.country" must be a "Country" instance.
So if i was not clear ,, what i need is exactly set foreign key to city when i create city ,, not create city and country,,
please any one had a solution help, because i tried many ways and read the django rest framework docs about this point but i didn't got it.
First of all, the raise_exception should be a boolean value (either True or False)
You could avoid this error by using inheriting the view class from ListCreateAPIView
from rest_framework.generics import ListCreateAPIView
class CityAPIView(ListCreateAPIView):
queryset = City.objects.all()
serializer_class = CitySerializer
permission_classes = [AllowAny, AllowAnonymous]
You don't want to use the post() method if you're using ListCreateAPIView, because DRF will take care of that part well.
Suggestion
Since you're dealing with CRUD functionalities of the model, you can use the DRF's ModelViewset class
you are not using the validated data to create a new city, just change this line:
serializer.create(validated_data=request.data)
to this:
serializer.save()
when you perform serializer.save(), the serializer will use its validated data.
also, DRF has a generic view(ListCreateAPIView) that covers your use-case.
Is it possible to get the current user in a model serializer? I'd like to do so without having to branch away from generics, as it's an otherwise simple task that must be done.
My model:
class Activity(models.Model):
number = models.PositiveIntegerField(
blank=True, null=True, help_text="Activity number. For record keeping only.")
instructions = models.TextField()
difficulty = models.ForeignKey(Difficulty)
categories = models.ManyToManyField(Category)
boosters = models.ManyToManyField(Booster)
class Meta():
verbose_name_plural = "Activities"
My serializer:
class ActivitySerializer(serializers.ModelSerializer):
class Meta:
model = Activity
And my view:
class ActivityDetail(generics.RetrieveUpdateDestroyAPIView):
queryset = Activity.objects.all()
serializer_class = ActivityDetailSerializer
How can I get the model returned, with an additional field user such that my response looks like this:
{
"id": 1,
"difficulty": 1,
"categories": [
1
],
"boosters": [
1
],
"current_user": 1 //Current authenticated user here
}
I found the answer looking through the DRF source code.
class ActivitySerializer(serializers.ModelSerializer):
# Create a custom method field
current_user = serializers.SerializerMethodField('_user')
# Use this method for the custom field
def _user(self, obj):
request = self.context.get('request', None)
if request:
return request.user
class Meta:
model = Activity
# Add our custom method to the fields of the serializer
fields = ('id','current_user')
The key is the fact that methods defined inside a ModelSerializer have access to their own context, which always includes the request (which contains a user when one is authenticated). Since my permissions are for only authenticated users, there should always be something here.
This can also be done in other built-in djangorestframework serializers.
As Braden Holt pointed out, if your user is still empty (ie _user is returning None), it may be because the serializer was not initialized with the request as part of the context. To fix this, simply add the request context when initializing the serializer:
serializer = ActivitySerializer(
data=request.data,
context={
'request': request
}
)
A context is passed to the serializer in REST framework, which contains the request by default. So you can just use self.context['request'].user inside your serializer.
I had a similar problem - I tried to save the model that consist user in, and when I tried to use
user = serializers.StringRelatedField(read_only=True, default=serializers.CurrentUserDefault()) like on official documentation - but it throws an error that user is 'null'. Rewrite the default create method and get a user from request helped for me:
class FavoriteApartmentsSerializer(serializers.ModelSerializer):
user = serializers.StringRelatedField(read_only=True, default=serializers.CurrentUserDefault())
class Meta:
model = FavoriteApartments
exclude = (
'date_added',
)
def create(self, validated_data):
favoriteApartment = FavoriteApartments(
apartment=validated_data['apartment'],
user=self.context['request'].user
)
favoriteApartment.save()
return favoriteApartment
I modified the request.data:
serializer = SectionSerializer(data=add_profile_data(request.data, request.user))
def add_profile_data(data, user):
data['user'] = user.profile.id
return data
I'm writing a REST API for my Django app, and can't get POST requests to work on one model.
Here's the model in question:
class ProjectNode(models.Model):
name = models.CharField(max_length=60)
place = models.CharField(max_length=150)
time_spent = models.BigIntegerField()
parent_project = models.ForeignKey(Project, related_name='tasks')
workers = models.ManyToManyField(User, related_name='tasks_can_do')
def __str__(self):
return self.name
The User model just holds a name field at the moment.
Here's my serializer for ProjectNode:
class ProjectNodeSerializer(serializers.ModelSerializer):
class Meta:
model = ProjectNode
fields = ('id', 'name', 'place', 'time_spent', 'workers',)
And here's the API view (from views.py):
class WebProjectNodeListView(generics.ListCreateAPIView):
queryset = ProjectNode.objects.all()
serializer_class = ProjectNodeSerializer
def pre_save(self, obj):
obj.parent_project = Project.objects.get(pk=self.request.DATA['parent_project'])
for worker_pk in self.request.DATA['workers']:
obj.workers.add(User.objects.get(pk=worker_pk))
obj.final_worker = User.objects.get(pk=self.request.DATA['final_workers'])
I tried a simpler version yesterday at first, which only had the Project ForeignKey relationship, and it seemed to work, so I thought that using add would work too, but I get an error when testing out the API with httpie (I already added some users and projects, and am sure I get their id's correctly).
Here's the request:
http POST :8000/api/tasks/ name="newtask" place="home" time_spent:=50 parent_project:=1 workers:=[1]
And I get this error:
"<ProjectNode: newtask>" needs to have a value for field "projectnode" before this many-to-many relationship can be used.
And the traceback also points to this line of code:
obj.workers.add(User.objects.get(id=worker_pk))
Now, I get the feeling that this is because I'm trying to update the relationship on the User object before a ProjectNode object is created in the database, but I'm not sure how to resolve this?
DRF doesn't works create models which are nested serializers objects or Many to Many fields.
So is necessary to override Serializer create method and create/get M2M models before create ProjectNode.
Try to override create(self, validated_data) in your serializer and work with your data inside this method..
Example:
My model Project has M2M relation with ProjectImages. In ProjectSerializer I override create method like this.
def create(self, validated_data):
try:
# Remove nested and M2m relationships from validated_data
images = validated_data.pop('projectimage_set') if 'projectimage_set' in validated_data else []
# Create project model
instance = Project(**validated_data)
if status:
instance.set_status(status)
project = instance.save()
# Create relations
for image in images:
ProjectImage.objects.create(project=project, **image)
except exceptions.ValidationError as e:
errors_messages = e.error_dict if hasattr(e, 'error_dict') else e.error_list
raise serializers.ValidationError(errors_messages)
return project
Hope this help!