Django Serializer getting attribute from another model - django

Question

I am working just for my experience and I stacked with the following problem. There are three models: Book, Chapter, and Publisher. Each model is related to one another with the foreign key.
class Book(models.Model):
name = models.CharField(max_length=64)
publisher = models.ForeignKey('Publisher', on_delete=models.CASCADE, null=True, blank=True)
def __str__(self):
return self.name
class Chapter(models.Model):
name = models.CharField(max_length=128)
book = models.ForeignKey(Book, related_name='books', on_delete=models.CASCADE)
class Publisher(models.Model):
title = models.CharField(max_length=128)
description = models.TextField()
def __str__(self):
return self.title
class Meta:
ordering = ['title']
I want to serialize the data in PublisherDetailSerializer which should show their books and all chapters related to their books.
Here are my serializers:
class BookSerializer(serializers.ModelSerializer):
class Meta:
model = Book
fields = ('id', 'name', 'publisher')
def to_representation(self, instance):
ret = super().to_representation(instance)
return ret
class ChapterSerializer(serializers.ModelSerializer):
id = serializers.IntegerField()
name = serializers.CharField(required=False)
location = serializers.SerializerMethodField()
class Meta:
model = Chapter
fields = ('id', 'name', 'location')
def get_location(self, instance):
serializer = BookSerializer(instance.author, context=self.context)
return serializer.data
class PublisherSerializer(serializers.HyperlinkedModelSerializer):
books = BookSerializer(many=True, read_only=True)
class Meta:
model = Publisher
fields = ('id', 'title', 'description', 'books')
class PublisherDetailSerializer(PublisherSerializer):
chapters = serializers.SerializerMethodField()
class Meta:
model = Publisher
fields = ('id', 'title', 'description', 'books', 'chapters')
def get_chapters(self, instance):
serializer = ChapterSerializer(Chapter.objects.filter(location=instance.books.name), many=True, context=self.context)
return serializer.data
def to_representation(self, instance):
ret = super().to_representation(instance)
return ret
Here is my view for Publisher:
class PublisherViewSet(MultiSerializerViewSetMixin, viewsets.ReadOnlyModelViewSet):
queryset = Publisher.objects.all()
serializer_class = PublisherSerializer
serializer_action_classes = {
'list': PublisherSerializer,
'retrieve': PublisherDetailSerializer,
}
Showing publishers and their books shows the right information in the browsable API, but I don't know how to get chapters through books. How should I approach it?

Answer 1

Notes:
the related_name in a models.ForeignKey is not what you thing it is. it is the attribute name to be used on the otherside of the relationship, see the below code
you can just nest the serializers as shown below
Models
class Publisher(models.Model):
title = models.CharField(max_length=128)
description = models.TextField()
class Book(models.Model):
name = models.CharField(max_length=128)
publisher = models.ForeignKey(Publisher, related_name='books', on_delete=models.CASCADE)
class Chapter(models.Model):
name = models.CharField(max_length=128)
book = models.ForeignKey(Book, related_name='chapters', on_delete=models.CASCADE)
Serializers
class ChapterSerializer(serializers.ModelSerializer):
id = serializers.IntegerField()
name = serializers.CharField(required=False)
class Meta:
model = Chapter
fields = ('id', 'name')
class BookSerializer(serializers.ModelSerializer):
chapters = ChapterSerializer(many=True, read_only=True)
class Meta:
model = Book
fields = ('id', 'name', 'chapters')
class PublisherSerializer(serializers.HyperlinkedModelSerializer):
books = BookSerializer(many=True, read_only=True)
class Meta:
model = Publisher
fields = ('id', 'title', 'description', 'books')