Models:
class Owner(models.Model):
name = models.CharField(max_length=255)
def __unicode__(self):
return self.name
class SomeThing(models.Model):
own_id = models.IntegerField(unique=True)
description = models.CharField(max_length=255, blank=True)
owner = models.ForeignKey(Owner, blank=True, null=True)
def __unicode__(self):
return self.description
Serializers:
class OwnerNameField(serializers.RelatedField):
def to_internal_value(self, data):
pass
def to_representation(self, value):
return value.name
def get_queryset(self):
queryset = self.queryset
if isinstance(queryset, (QuerySet, Manager)):
queryset = queryset.all()
lista = [Owner(name="------------")]
lista.extend(queryset)
return lista
class OwnerSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Owner
fields = ('name', 'id')
class ThingSerializer(serializers.ModelSerializer):
owner = OwnerNameField(queryset=Owner.objects.all())
class Meta:
model = SomeThing
fields = ('own_id', 'description', 'owner')
Basically it works as intended. But when i add some fields to Owner class i would like to see all these fields in output of ThingSerializer (and be able to parse them - string doesn't suit here). I could change field owner to owner = OwnerSerializer() which gives me what i need. But when i want to add SomeThing object (tested in API browser) i also need add new Owner object - and i don't want it, i want use existing Owner object. How can i achieve it?
Finally i got it. This question describes exactly my problem and provided answers work as a charm!
Related
I have two models:
class Restaurant(models.Model):
adress = models.CharField(max_length=240)
name = models.CharField(max_length=140)
class RestaurantReview(models.Model):
review_author = models.ForeignKey(settings.AUTH_USER_MODEL,
on_delete=models.CASCADE)
restaurant = models.ForeignKey(Restaurant, on_delete=models.CASCADE)
created_at = models.DateTimeField(auto_now_add=True)
I use DRF and front-end I need the values of the fields to use in Vue.je templates. Here is my serializer:
class RestaurantReviewSerializer(serializers.ModelSerializer):
restaurant_name = serializers.CharField(source='restaurant.name')
restaurant_adress = serializers.CharField(source='restaurant.adress')
created_at = serializers.SerializerMethodField()
review_author = serializers.StringRelatedField(read_only=True)
class Meta:
model = RestaurantReview
fields = ('id','restaurant_name','restaurant_adress','created_at','review_author')
def get_created_at(self, instance):
return instance.created_at.strftime("%d %B, %Y")
I get the right data I need but my problem is now I can't update/create new models. As suggested I added ('read_only'=True) but the result is the same.
Should I use to_representation to get the same CRUD posibilities than with:
class RestaurantReviewSerializer(serializers.ModelSerializer):
class Meta:
model = RestaurantReview
field = fields = '__all__'
But with the benefit to have for exemple 'restaurant' named after its name and not its ID so I can use it in my template?
Follow to comment above.
Use single viewset and override get_serializer_class. No other thing to change.
class RestaurantReviewViewSet(viewsets.ModelViewSet):
queryset = RestaurantReview.objects.all()
def get_serializer_class(self):
if self.request.method == 'GET':
return RestaurantReviewGETSerializer # your above serializer
else:
return RestaurantReviewSerializer # default serializer
How to update more than one object of different model types from one end point. I tried it many ways but i still fails.I tried through nested serializer and create method, but it is still not working
class Student(models.Model):
name = models.CharField(max_length=300)
sex = models.CharField(choices=SEX_CHOICES,max_length=255,
null=True)
Category = models.CharField(max_length=100, null=True)
def __str__(self):
return self.name
class Registration(models.Model):
registration_no = models.CharField(max_length=255,
unique=True)
student = models.OneToOneField(Student,
on_delete= models.CASCADE, related_name='registrations')
def __str__(self):
return self.registration_no
class RegistrationSerializer(serializers.ModelSerializer):
class Meta:
model = Registration
fields = '__all__'
class StudentSerializer(serializers.ModelSerializer):
class Meta:
model = Student
fields = '__all__'
class StudentDataMigrateSerializer(serializers.Serializer):
student = StudentSerializer()
registation = RegistrationSerializer()
In Django Rest Framework by default the nested serializers are read only. To have a writable nested serializer you need to implement create() and/or update() methods.
Take a look at the official documentation https://www.django-rest-framework.org/api-guide/relations/#writable-nested-serializers
class StudentDataMigrateSerializer(serializers.Serializer):
student = StudentSerializer()
registation = RegistrationSerializer()
def create(self, validated_data):
# save the data
I'm using a Polymorphic model for setting up notifications:
My models:
class Notification(PolymorphicModel):
id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
created_by = models.ForeignKey(ElsUser, on_delete=models.CASCADE, default=None, related_name="creatednotifications")
created_on = models.DateTimeField(default=timezone.now)
created_for = models.ForeignKey(ElsUser, on_delete=models.CASCADE, default=None, related_name="receivednotifications")
read = models.DateTimeField(default=None, null=True, blank=True)
message = models.CharField(default=None, blank=True, null=True, max_length=800)
#property
def total(self):
return self.objects.filter(created_for=self.request.user).count()
#property
def unread(self):
return self.objects.filter(created_for=self.request.user,read=None).count()
#property
def read(self):
return self.objects.filter(created_for=self.request.user).exclude(read=None).count()
class WorkflowNotification(Notification):
# permission_transition = models.ForeignKey(WorkflowStatePermissionTransition, on_delete=models.CASCADE)
action = models.ForeignKey(UserAction, on_delete=models.CASCADE)
Currently i have just one model WorkFlowNotification inheriting from the Polymorphic model,but many would be there in the future.
Im trying to get the count(total) of notifications for the logged in user in the API ..total is given as property field to help in the same
my serializer:
class NotificationSerializer(serializers.ModelSerializer):
total = serializers.ReadOnlyField()
read = serializers.ReadOnlyField()
unread = serializers.ReadOnlyField()
class Meta:
model = Notification
fields = ['id', 'total','read', 'unread']
In the view:
class NotificationsMeta(generics.ListAPIView):
serializer_class = NotificationSerializer
queryset = Notification.objects.all()
When i try to run the server it shows:
Got AttributeError when attempting to get a value for field `total` on serializer `NotificationSerializer`.
The serializer field might be named incorrectly and not match any attribute or key on the `WorkflowNotification` instance.
Original exception text was: Manager isn't accessible via WorkflowNotification instances.
Since you need the 'meta data' only, what is the use of making a model serializer? Or any serializer, for that matter? Serializers will give you serialized instances of the objects of your model. So if you have multiple objects, you will get multiple serialized objects in response.
Just make your view a normal APIView. Since there is no necessity of serializing anything.
class NotificationsMeta(APIView):
def get(self, request, format=None):
qs = Notification.objects.filter(created_for=self.request.user)
response = {
'total': qs.count(),
'read': qs.filter(read=None).count(),
'unread': qs.exclude(read=None).count()
}
return Response(response)
Now remove those property functions from your model.
I didn't test your queries, just copied them from your model. You will need to check if they are working properly. Hope this helps.
I am not sure about how calling a model property who is responsible for querying in model can give appropriate data from serializer. Unfortunately i do have knowledge gap about that. I am thinking about an alternative solution. I hope following should work.
class NotificationSerializer(serializers.ModelSerializer):
total = serializers.serializers.SerializerMethodField()
read = serializers.ReadOnlyField()
unread = serializers.ReadOnlyField()
class Meta:
model = Notification
fields = ['read', 'unread']
def get_total(self, obj):
user = self.context['request'].user
return Notification.objects.filter(created_for=user).count()
If this work then you can able to do similar kind of thing for read and unread too.
In order to get notification for current_user we need to overwrite get_queryset from view.
class NotificationsMeta(generics.ListAPIView):
serializer_class = NotificationSerializer
def get_queryset(self):
return Notification.objects.filter(created_for=self.request.user)
I use django rest in my project and until now for list of objects I used ListSerializer, when I needed to have min length and max length of list I googled and reached to ListField.
Before that my code worked fined without any error and misbehavior. Now I use ListField for my list field serializer, But I didn't get when to use ListSerializer? Can someone explain the difference between ListSerializer and FieldSerializer?
My sample code with ListSerializer:
tags = serializers.ListSerializer(child=serializers.CharField(allow_blank=False), required=False)
My sample code with ListField:
open_hour = serializers.ListField(child=serializers.DictField(), max_length=7, min_length=7)
Disclaimer: This answer is not complete
Can someone explain the difference between ListSerializer and
FieldSerializer?
I assume the question is difference between serializers.ListSerializer and serializers.ListField
Suppose we have two models as
class Musician(models.Model):
first_name = models.CharField(max_length=50)
last_name = models.CharField(max_length=50)
instrument = models.CharField(max_length=100)
def __str__(self):
return f'{self.first_name} {self.last_name}'
class Album(models.Model):
artist = models.ForeignKey(Musician, on_delete=models.CASCADE)
name = models.CharField(max_length=100)
release_date = models.DateField()
num_stars = models.IntegerField()
def __str__(self):
return f'{self.name} : {self.artist}'
and serializer as
class AlbumSerializer(serializers.ModelSerializer):
artist = serializers.StringRelatedField()
class Meta:
fields = '__all__'
model = Album
class MusicianSerializer(serializers.ModelSerializer):
AlbumSerializer(many=True, source='album_set')
class Meta:
fields = '__all__'
model = Musician
ListSerializer
As stated in official DRF doc
When a serializer is instantiated and many=True is passed, a
ListSerializer instance will be created. The serializer class then
becomes a child of the parent ListSerializer
For example, we could re-write the MusicianSerializer with ListSerializer as
class MusicianSerializer(serializers.ModelSerializer):
albums = serializers.ListSerializer(child=AlbumSerializer(), source='album_set')
class Meta:
fields = '__all__'
model = Musician
it would produce the results same as before. But, if we are trying to use ListField instead of ListSerializer It will raise an error
'RelatedManager' object is not iterable
When I checked the source code, I found that both ListSerializer and ListField are inherited from the same class (parent and grand parent are same)
I ran into this same problem and I believe I found a solution!
The trick is you need to create a new Serializer that inherits the ListSerializer class and override the to_representation() method to output your desired format.
If you look at the DRF source code for ListSerializer you can see the default to_representation() method looks like the following...
def to_representation(self, data):
"""
List of object instances -> List of dicts of primitive datatypes.
"""
# Dealing with nested relationships, data can be a Manager,
# so, first get a queryset from the Manager if needed
iterable = data.all() if isinstance(data, models.Manager) else data
return [
self.child.to_representation(item) for item in iterable
]
Example
models
class Musician(models.Model):
first_name = models.CharField(max_length=50)
last_name = models.CharField(max_length=50)
instrument = models.CharField(max_length=100)
def __str__(self):
return f'{self.first_name} {self.last_name}'
class Album(models.Model):
artist = models.ForeignKey(Musician, on_delete=models.CASCADE)
name = models.CharField(max_length=100)
release_date = models.DateField()
num_stars = models.IntegerField()
def __str__(self):
return f'{self.name} : {self.artist}'
serializers
class AlbumSerializer(serializers.ModelSerializer):
artist = serializers.StringRelatedField()
class Meta:
fields = '__all__'
model = Album
class AlbumKeyValueSerializer(serializers.ListSerializer):
def to_representation(self, data):
reaction_count_set = {}
for item in data.all():
reaction_count_set[item.name] = item.artist
return reaction_count_set
class MusicianSerializer(serializers.ModelSerializer):
AlbumKeyValueSerializer(child=AlbumSerializer(), source='album_set')
class Meta:
fields = '__all__'
model = Musician
I have model Person - from another database
I copied all person_id to custom_id.
models.py
class Employee(models.Model):
custom_id = models.CharField(max_length=20, unique=True)
#property
def person(self):
return Person.objects.get(person_id='%s' % self.custom_id)
def __str__(self):
return '%s' % self.custom_id
class Task(models.Model):
employee = models.ManyToManyField(Employee, blank=True, null=True)
task = models.CharField(max_length=100)
comment = models.CharField(max_length=200)
def __str__(self):
return '%s' % self.task
I add my method person() to Employee which allow me to access other objects model in another database:
So basically when I type this in shell:
Employee.objects.get(custom_id='123').person.full_name
u'Adam Dylan'
I have a ModelForm which use ModelMultipleChoiceField
forms.py
class TaskCreateForm(forms.ModelForm):
employee = forms.ModelMultipleChoiceField(queryset=Employee.objects.all())
class Meta:
model = Task
But Employee.objects.all() returns bunch of custom_id's.
What I want is to show in form "Employee(..).person.full_name" but saving only custom_id's.
I am not sure why you think the answer I gave to your other question does not work here. Did you try the following? If it does not work, how exactly does it fail?
class EmployeeMultipleChoiceField(ModelMultipleChoiceField):
def label_from_instance(self, obj):
return obj.person.full_name
class TaskCreateForm(forms.ModelForm):
employee = EmployeeMultipleChoiceField(queryset=Employee.objects.all())
class Meta:
model = Task