I am trying to create an API with Artists and Songs, with a ManyToMany relationship between the two. Using the API to create a Song with an Artist that is not in the database works fine. The problem arises when I attempt to use the POST method to create a new Song with an Artist that already exists in the database. I tried overwriting the SongSerializer create() method using get_or_create() based on another post here, but I kept getting Bad Request errors when the Artist already exists in the database. The relevant code snippets:
models.py
class Artist(models.Model):
artist_name = models.CharField(max_length=200, unique=True)
class Meta:
ordering = ['artist_name']
def __str__(self):
return self.artist_name
class Song(models.Model):
song_title = models.CharField(max_length=200)
artists = models.ManyToManyField(Artist, related_name='songs')
class Meta:
ordering = ['song_title']
def __str__(self):
return self.song_title
serializers.py
class ArtistNameSerializer(serializers.ModelSerializer):
class Meta:
model = Artist
fields = ('artist_name',)
def to_representation(self, value):
return value.artist_name
class SongTitleSerializer(serializers.ModelSerializer):
songs = serializers.PrimaryKeyRelatedField(read_only=True, many=True)
def to_representation(self, value):
return value.song_title
class Meta:
model = Song
fields = ('songs',)
class ArtistSerializer(serializers.HyperlinkedModelSerializer):
songs = SongTitleSerializer(read_only=True, many=True)
class Meta:
model = Artist
fields = ('id', 'artist_name', 'songs')
class SongSerializer(serializers.HyperlinkedModelSerializer):
artists = ArtistNameSerializer(many=True)
class Meta:
model = Song
fields = ('id', 'song_title', 'artists',)
def create(self, validated_data):
artist_data = validated_data.pop('artists')
song = Song.objects.create(**validated_data)
song.save()
for artist_item in artist_data:
a, created = Artist.objects.get_or_create(artist_name=artist_item['artist_name'])
song.artists.add(a)
return song
I've done some tests and it looks like the program doesn't even go into the create() method I'm using, going straight to showing me the Bad Request error. What am I missing? Thanks in advance!
On you Artist model you have a constrain on the artist_model field (unique=True)
if you print the serializer in question with:
print(SongSerializer())
you get something like this:
SongSerializer():
id = IntegerField(label='ID', read_only=True)
song_title = CharField(max_length=200)
artists = ArtistNameSerializer(many=True):
artist_name = CharField(max_length=200, validators=[<UniqueValidator(queryset=Artist.objects.all())>])
under the artist_name field is a Validator "UniqueValidator"
so in case of a write operation you can disable the validator in the serializer with:
class ArtistNameSerializer(serializers.ModelSerializer):
class Meta:
model = models.Artist
fields = ('artist_name',)
extra_kwargs = {
'artist_name': {
'validators': [],
}
}
hope this help..
Related
I'm currently working on a Django project, I'm new at this and it's difficult to find clear documentation about this.
My issue is very simple, I want at the creation of my model, automatically associate another model through a ManyToMany relationship.
Here goes the code :
Model :
class Favorite(models.Model):
uuid = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
title = models.CharField(max_length=60, blank=False)
estates = models.ManyToManyField(Estate, blank=True)
Serializer :
class FavoriteSerializer(serializers.ModelSerializer):
estates = EstateSerializer(read_only=True, many=True)
class Meta:
model = Favorite
fields = ['uuid', 'title', 'estates']
def create(self, validated_data):
instance = super(FavoriteSerializer, self).create(validated_data)
instance.save()
return instance
ViewSet :
class MyFavoriteEstatesListViewSet(viewsets.ModelViewSet):
serializer_class = FavoriteSerializer
def get_queryset(self):
return Favorite.objects.filter(users__id=self.request.user.id)
I'm currently sending something like this through a POST :
{"title": "some title", "estate_uuid": "XXX"}
I just wanted to instantiate my Estate model with the UUID I just sent and adding it with
favorite.estates.add(estate)
How can I achieve this ?
Thanks for your help !
I think you can try something like this:
class EstateField(serializers.RelatedField):
def to_representation(self, obj):
return EstateSerializer(obj).data
def to_internal_value(self, data):
return Estate.objects.get(pk=data)
class FavoriteSerializer(serializers.ModelSerializer):
estates = EstateField(many=True, queryset=Estate.objects.all())
class Meta:
model = Favorite
fields = ['uuid', 'title', 'estates']
I am using Custom Fields to represent the data as dictionary, but take input as uuid.
I'm using Django 3.0 and I have a serializer using django-rest-framework. Let's say that for example I have a Forum object. Each forum has an owner that is a user.
In my GET /forums/ endpoint, I'd like to just have the owner_id. However, in my GET /forums/<forum_id>/ endpoint I'd like to return the entire embedded object.
Is there any way to have one serializer support both of these scenarios? If not, I would hate to have to make two serializers just to support this.
class ForumSerializer(serializers.ModelSerializer, compact=True):
if self.compact is False:
owner = UserSerializer(source='owner', read_only=True)
else:
owner_id = serializers.UUIDField(source='owner_id')
...
How can I achieve this compact thing?
class Meta:
fields = [...]
read_only_fields = ['owner', 'owner_id']
You can add a SerializerMethodField like this:
class ForumSerializer(serializers.ModelSerializer):
owner = serializer.SerializerMethodField()
def get_owner(self, obj):
if self.context['is_compact'] == True:
return obj.owner.pk
else:
return UserSerializer(obj.owner).data
class Meta:
model = YourModel
fields = '__all__'
# Usage in view
serializer = ForumSerializer(context={'is_compact':True})
I am passing is_compact value through serializer's extra context.
create two serializer classes
class ForumSerializerId(ModelSerializer):
class Meta:
model = Forum
fields = ['forum_id']
class ForumSerializerDetail(ModelSerializer):
class Meta:
model = Forum
on your view.py
forums(request):
forum_list = Forum.objects.all()
forum_serializer = ForumSerializerId(forum_list,many=True)
return Response({"form":forum_serializer.data})
forum_detail(request,pk):
forum = get_object_or_404(Forum,pk)
forum_serializer = ForumSerializerDetail(forum)
return Response({"form":forum_serializer.data})
These are simplified versions of my models (the user model is just an id and name)
class Convo(models.Model):
owner = models.ForeignKey(User, on_delete=models.CASCADE, related_name='convo_owner')
users = models.ManyToManyField(User, through='Convo_user')
class Convo_user (models.Model):
user = models.ForeignKey(UserProfile, on_delete=models.CASCADE)
convo = models.ForeignKey(Convo, on_delete=models.CASCADE)
class Comments(models.Model):
name = models.CharField(max_length=255)
content = models.TextField(max_length=1024)
convo = models.ForeignKey(Convo, on_delete=models.CASCADE)
This is my view
class ConvoViewSet(viewsets.ModelViewSet):
serializer_class = serializers.ConvoSerializer
def get_queryset(self):
return None
def list(self, request):
curr_user = request.user.id
# Collecting the list of conversations
conversations = models.Conversation.object.filter(ConvoUser__user_id=request.user.id)
#Getting list of conversation id's
conv_ids = list(conversations.values_list('id', flat=True).order_by('id'))
#Getting list of relevant comments
comments = models.Comments.objects.filter(conversation_id__in=conv_ids)
return Response(self.get_serializer(conversations, many=True).data)
And my current serializer
class ConvoSerializer(serializers.ModelSerializer):
"""A serializer for messaging objects"""
# access = AccessSerializer(many=True)
# model = models.Comments
# fields = ('id', 'name', 'content', 'convo_id')
class Meta:
model = models.Convo
fields = ('id', 'owner_id')
The current response I get is of the form
[
{
"id": 1,
"owner_id": 32
}, ...
]
But I would like to add a comments field that shows all the properties of comments into the response, so basically everything in the second queryset (called comments) and I'm not sure how to go about this at all. (I retrieve the comments in the way I do because I'm trying to minimize the calls to the database). Would I need to create a new view for comments, make its own serializer and then somehow combine them into the serializer for the convo?
The way you've set up your models, you can access the comments of each Convo through Django's ORM by using convo_object.comments_set.all(), so you could set up your ConvoSerializer to access that instance's comments, like this:
class ConvoSerializer(serializers.ModelSerializer):
"""A serializer for messaging objects"""
comments_set = CommentSerializer(many=True)
class Meta:
model = models.Convo
fields = ('id', 'owner_id', 'comments_set')
and then you define your CommentSerializer like:
class CommentSerializer(serializers.ModelSerializer):
class Meta:
model = models.Comments
fields = ('id', 'name', 'content')
No data appears because my serializers are using the default database, not sure why but a step forward
EDIT:
Django: Database used for prefetch_related is not the same that the parent query Provided me the correct answer, I was able to choose the database with this method because for some reason inner queries use the default DB
I'm trying to create a custom serializer method that counts the number of passed and failed quizzes from my QuizResults model. A failed quiz is under .7 and a passed quiz is .7 or over.
I want to be able to look into the Users QuizResult and count the number of passed quizzes(.7 or over). I would then duplicate the method to count the failed quizzes (under .7).
So far I don't have much idea on how to do so. I want to be able to grab the percent_correct field of the model and do a calculation and add it to a field in the serializer called "quiz_passed".
Here is my QuizResult model:
class QuizResult(models.Model):
quiz = models.ForeignKey(Quiz)
user = models.ForeignKey(User, related_name='quiz_parent')
percent_correct = models.FloatField(validators=[MinValueValidator(0.0), MaxValueValidator(1.0)])
date = models.DateTimeField(auto_now_add=True)
def __str__(self):
return 'Quiz Results for : ' + self.quiz.title
Here is my serializer:
class ProfileSerializer(serializers.HyperlinkedModelSerializer):
todo_count = serializers.IntegerField(source='todo_parent.count', read_only=True)
discussion_count = serializers.IntegerField(source='comment_parent.count', read_only=True)
quiz_passed = serializers.SerializerMethodField()
class Meta:
model = User
fields = ('todo_count', 'discussion_count', 'quiz_passed', 'username', )
def get_quiz_passed(self, obj):
return passed
Any help is appreciated.
Edit:
I extended the User model and added a model method like you suggested.
class Profile(User):
def get_quizzes_passed_count(self):
return self.quiz_parent.filter(percent_correct__gte=0.8).count()
I then added your suggestion to my ProfileSerializer.
class ProfileSerializer(serializers.HyperlinkedModelSerializer):
todo_count = serializers.IntegerField(source='todo_parent.count', read_only=True)
discussion_count = serializers.IntegerField(source='comment_parent.count', read_only=True)
num_quizzes_passed = serializers.ReadOnlyField(source="get_quizzes_passed_count")
class Meta:
model = Profile
fields = ('todo_count', 'discussion_count', 'num_quizzes_passed', 'username')
Unfortunately when I add this nothing appears in the framework once these have been added. Any suggestions? Thank you.
You can use a model method on the user model to count that user's number of passed quizzes:
class User(models.model):
# rest of your User attributes
def get_quizzes_passed_count(self):
return self.quiz_parent.filter(percent_correct__gte=0.7).count()
Then add that to your serializer using a DRF ReadOnlyField to serialize that method:
class ProfileSerializer(serializers.HyperlinkedModelSerializer):
todo_count = serializers.IntegerField(
source='todo_parent.count', read_only=True
)
discussion_count = serializers.IntegerField(
source='comment_parent.count', read_only=True
)
quiz_passed = serializers.SerializerMethodField()
num_quizzes_passed = serializers.ReadOnlyField(source="get_quizzes_passed_count")
class Meta:
model = User
fields = ('todo_count', 'discussion_count', 'quiz_passed', 'username', )
def get_quiz_passed(self, obj):
return passed
You can duplicate this for the number of failed quizzes.
I'm developing RESTFul services with DRF and I have multiple databases depending on the country (see my last question here)
I'm having a problem now with relationships, I have two models: Category and SubCategory:
class SubCategory(models.Model):
objects = CountryQuerySet.as_manager()
id = models.AutoField(primary_key=True,db_column='sub_category_id')
name = models.TextField()
female_items_in_category = models.BooleanField()
male_items_in_category = models.BooleanField()
kids_items_in_category = models.BooleanField()
category = models.ForeignKey('Category')
class Meta:
managed = True
db_table = Constants().SUBCATEGORY
And the serializer is:
class SubCategorySerializer(serializers.ModelSerializer):
category = PrimaryKeyRelatedField(queryset=Category.objects.using('es').all())
class Meta:
model = SubCategory
fields = ('id', 'name','female_items_in_category','male_items_in_category','kids_items_in_category','category')
If I don't set the queryset with the proper country it fails, because it doesn't know where to get the category.
Here the problem
I already set the country in the serializer context (in the ModelViewSet):
def get_serializer_context(self):
return {Constants().COUNTRY: self.kwargs.get(Constants().COUNTRY)}
But I can not find the proper way to get the self.context.get(Constants().COUNTRY) in the serializer.
Do you any have an idea to solve this? Thanks!
Well, I found a solution to my problem: I overwrite the method get_fields in the serializer:
def get_fields(self, *args, **kwargs):
fields = super(SubCategorySerializer, self).get_fields()
country = self.context.get(Constants().COUNTRY)
qs = Category.objects.using(country).all()
fields['category'].queryset = qs
return fields
And that works!