Getting field value with DjangoRestFramework serializer - django

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

Related

Django list data from dfiferent models in List View with correct ordering

Heys guys.. I am making a Django project which is a simple clone of Twitter.. Got the idea from Justin Mitchell's Udemy course..
So i implemented a Tweet model and a Retweet model which has ForeignKey to the original Tweet and the User..
The thing is that in the homepage i want both the Tweets and Retweets to show and in the order they were created..
I am using Django Rest Framework for the CRUD functionality of Tweet using ModelViewSet
Any idea on how i achieve that using Rest Framework or if that isn't possible could you please give me some other idea..
Thank you in advance..
models.py
class Tweet(models.Model):
content = models.CharField(max_length=140)
user = models.ForeignKey(User, on_delete=models.CASCADE)
created_on = models.DateTimeField(auto_now_add=True)
updated_on = models.DateTimeField(auto_now=True)
class Meta:
ordering = "-created_on", "content", "user",
def __str__(self):
return self.content
def get_absolute_url(self):
return reverse("tweet_api:tweet-detail", args=[self.id])
class Retweet(models.Model):
tweet = models.ForeignKey(Tweet, on_delete=models.CASCADE, related_name="retweet")
user = models.ForeignKey(User, on_delete=models.CASCADE)
created_on = models.DateTimeField(auto_now_add=True)
class Meta:
ordering = "-created_on", "user",
def __str__(self):
return self.tweet.content
serializers.py
class TweetSerializer(serializers.ModelSerializer):
user = UserSerializer(read_only=True)
created_on = serializers.SerializerMethodField()
date_display = serializers.SerializerMethodField()
class Meta:
model = models.Tweet
fields = "id", "content", "created_on", "date_display", "user",
def get_created_on(self, obj):
return obj.created_on.strftime("%I:%M %p - %d %b %Y")
def get_date_display(self, obj):
obj_date = obj.created_on
days = (timezone.datetime.now() - obj_date).days
if days > 0:
return obj_date.strftime("%d %b")
else:
return naturaltime(obj_date)
class RetweetSerializer(serializers.ModelSerializer):
tweet = TweetSerializer()
user = UserSerializer(read_only=True)
date_display = serializers.SerializerMethodField()
class Meta:
model = models.Retweet
fields = "id", "tweet", "user", "created_on", "date_display",
def get_date_display(self, obj):
obj_date = obj.created_on
days = (timezone.datetime.now() - obj_date).days
if days > 0:
return obj_date.strftime("%d %b")
else:
return naturaltime(obj_date)
views.py
class TweetViewSet(ModelViewSet):
serializer_class = serializers.TweetSerializer
queryset = models.Tweet.objects.all()
pagination_class = DefaultPagination
filter_backends = filters.SearchFilter,
search_fields = "content", "user__username", "user__first_name", "user__last_name",
def perform_create(self, serialiazer):
return serialiazer.save(user=self.request.user)
class RetweetViewSet(ModelViewSet):
serializer_class = serializers.RetweetSerializer
queryset = models.Retweet.objects.all()
pagination_class = DefaultPagination
filter_backends = filters.SearchFilter,
search_fields = "tweet__content", "user__username", "user__first_name", "
As Tweet and Retweet data reside on completely different models, what you want to do is not simple with your current model structure. To combine them in a single view, you'd need to override many things on ViewSet, and do the operations like sorting in-memory, which would not be scalable. One possible solution could be to use model inheritance, have a base model for both Tweet and Retweet, and build your serialzier and view set on that model. A model structure like the following could be used:
class Post(models.Model):
"""
Base model for user posts
"""
user = models.ForeignKey(User, on_delete=models.CASCADE)
created_on = models.DateTimeField(auto_now_add=True)
class Tweet(Post):
content = models.CharField(max_length=140)
updated_on = models.DateTimeField(auto_now=True)
class Retweet(Post):
tweet = models.ForeignKey(Tweet, on_delete=models.CASCADE, related_name="retweet")
With these models in-place, you can create a PostSerializer and PostViewSet, and use these only for listing posts, you can keep using Tweet and Retweet views and serializers for creating and updating.

How to add and update data into foreign key field in django model

I have two models which is related to a forignkey.
class BikeModel(models.Model):
City = models.ForeignKey(CityForBike, on_delete=models.CASCADE)
BikeModels = models.CharField(default='', max_length=50)
Image = models.ImageField(upload_to='bike_images', blank=True, null=True, default='https://www.urbandrive.co.in/Admin/API/UploadedFiles/CarImage/44b150b3-f61a-41b5-afd8-34ded18fa980.png')
class Meta:
verbose_name_plural = 'BikeModels'
def __str__(self):
return self.BikeModels
class CityForBike(models.Model):
CityForCars = models.CharField(default="",max_length=50)
class Meta:
verbose_name_plural = 'CityForBikes'
def __str__(self):
return self.CityForCars
and i want to insert data to BikeModel. but it gives me error.
AssertionError: You cannot call `.save()` on a serializer with invalid data.
I want to know how to insert data to forign key field.
if request.method == 'POST':
import pdb;
pdb.set_trace()
input_data = json.loads(request.read().decode('utf-8'))
print(input_data)
serializer = serializers.BikeModelSerializer(data=input_data)
if serializer.is_valid():
serializer.save()
return render(request, "bike_model_add.html", {'car_city': car_city}, status=200)
And this is the data i am sending.
{'City': 'testo', 'BikeModels': 'ds'}
this is my serializers
class CityForBikeSerializer(serializers.ModelSerializer):
class Meta:
model = models.CityForBike
fields = '__all__'
class BikeModelSerializer(serializers.ModelSerializer):
class Meta:
model = models.BikeModel
fields = '__all__'
If you want to identify cities by their name in the bike serializer, you need to use SlugRelatedField.
class BikeModelSerializer(serializers.ModelSerializer):
City = serializers.SlugRelatedField(slug_field='CityForCars')
class Meta:
model = models.BikeModel
fields = '__all__'

DRF ListSerializer and ListField

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

django rest framework : nested model get not working. 'str' object has no attribute 'values'

I have a customer model in Bcustomer app that extends the django User model, So I will save the basic details such as name in User table and the remaining data (city, etc) in customer table.
Saving is working perfectly. But now it is showing the following error when I call the GET method.
AttributeError at /api/v1/customer 'str' object has no attribute 'values'
Request Method: GET
bcustomer/models.py
class BCustomer(models.Model):
customer = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, primary_key=True, blank=True )
address = models.CharField(max_length=50)
city = models.CharField(max_length=256)
state = models.CharField(max_length=50)
user = models.ForeignKey(settings.AUTH_USER_MODEL, db_index=True, on_delete=models.CASCADE, related_name='customer_creator')
# more fields to go
def __str__(self):
# return str(self.name) (This should print first and last name in User model)
class Meta:
app_label = 'bcustomer'
bcusomer/serializers.py
class CustomerDetailsSerializer(serializers.ModelSerializer):
class Meta:
model = BCustomer
fields = ('city', 'phone')
class CustomerSerializer(serializers.ModelSerializer):
customer_details = CustomerDetailsSerializer()
class Meta:
model = get_user_model()
fields = ('id','first_name', 'email', 'customer_details')
def create(self, validated_data):
request = self.context.get('request')
customer_details_data = validated_data.pop('customer_details')
customer_user = get_user_model().objects.create(**validated_data)
BCustomer.objects.create(customer=customer_user, user=request.user, **customer_details_data)
customer_user.customer_details = customer_details_data
return customer_user
class CustomerListSerializer(serializers.ModelSerializer):
model = get_user_model()
fields = '__all__'
class Meta:
model = get_user_model()
fields = '__all__'
bcustomer/views.py
class CustomerViewSet(viewsets.ModelViewSet):
customer_photo_thumb = BCustomer.get_thumbnail_url
permission_classes = [permissions.IsAuthenticated, TokenHasReadWriteScope]
queryset = BCustomer.objects.all()
serializer_class = CustomerSerializer
def get_queryset(self):
queryset = BCustomer.objects.all()
return queryset
def get_serializer_class(self):
if self.action == 'list' or self.action == 'retrieve':
return CustomerListSerializer
return CustomerSerializer
bcustomer/urls.py
router.register(r'customer', views.CustomerViewSet, 'customers')
Data post parameter format
{
"first_name":"Myname",
"email":"testemail#gmail.com",
"customer_details": {
"city":"citys",
"phone":"04722874567",
}
}
You should remove model and fields from CustomListSerializer
class CustomerListSerializer(serializers.ModelSerializer):
class Meta:
model = get_user_model()
fields = '__all__'
customer_details = CustomerDetailsSerializer()
You need to set the source argument to point to the user model's customer. Most probably:
customer_details = CustomerDetailsSerializer(source='customer')
(or maybe source='bcustomer', not sure if it reversed the field name or class name).
On a side not, you should not need the ListSerializer at all. The list method will call the serializer with the many=True argument on CustomerSerializer which will create the ListSerializer appropriately.

Nested objects save in DRF

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!