How can I implement a nested representation using intermediate model? - django

Question

I am quite new to Django and Django Rest Framework.
What I like to do in my project is display intermediate model's information using ListAPIView and also include detailed information about another Model connected to the intermediate model with a Foreign Key Relationship in the form of nested representation.
I have 3 models in my project, User, Content, Bookmark.
My model goes like below.
class MyUser(AbstractBaseUser, PermissionsMixin):
email = models.EmailField(unique=True)
username = models.CharField(max_length=50)
joined_date = models.DateTimeField(auto_now_add=True)
is_staff = models.BooleanField(default=False)
is_superuser = models.BooleanField(default=False)
facebook_id = models.CharField(max_length=50, blank=True)
is_facebook = models.BooleanField(default=False)
is_active = models.BooleanField(default=False)
class Content(models.Model):
seq = models.CharField(max_length=20, unique=True)
title = models.CharField(max_length=100, null=True)
start_date = models.DateField(null=True)
end_date = models.DateField(null=True)
place = models.TextField(null=True)
realm_name = models.TextField(null=True)
area = models.TextField(null=True)
price = models.TextField(null=True)
content = models.TextField(null=True)
ticket_url = models.TextField(null=True)
phone = models.TextField(null=True)
thumbnail = models.TextField(null=True)
bookmarks = models.ManyToManyField(User, through='Bookmark')
The last model, an intermediate model to connect MyUser and Content.
class Bookmark(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE)
content = models.ForeignKey(Content, on_delete=models.CASCADE)
created_date = models.DateTimeField(auto_now_add=True)
description = models.CharField(max_length=200, null=True)
class Meta:
unique_together = (('user', 'content'),)
ordering = ['-created_date']
def __str__(self):
return '{} bookmarked by user {}'.format(self.content, self.user)
I want to use BookmarkListAPIView to show certain user's bookmark information and some detailed information of Contents that the user added such as title, price, and start_date.
Below is my Serializer and ListAPIView.
class BookmarkListView(generics.ListAPIView):
queryset = Bookmark.objects.all()
serializer_class = BookmarkSerializer
pagination_class = DefaultResultsSetPagination
def get_queryset(self):
user = self.request.user
return user.bookmark_set.all().order_by('-created_date')
class BookmarkedContentSerializer(serializers.ModelSerializer):
class Meta:
model = Content
fields = ('title', 'start_date', 'price')
class BookmarkSerializer(serializers.ModelSerializer):
content = BookmarkedContentSerializer(many=True, read_only=True)
#bookmark = BookmarkedContentSerializer(many=True, read_only=True)
class Meta:
model = Bookmark
fields = ('content', 'user')
Currently, the API gives me results just like below.
{
"count": 6,
"next": null,
"previous": null,
"results": [
{
"content": 8,
"user": 4
},
{
"content": 6,
"user": 4
},
{
"content": 1,
"user": 4
},
{
"content": 2,
"user": 4
},
{
"content": 3,
"user": 4
},
{
"content": 10,
"user": 4
}
]
}
As mentioned above, I want to use the content ID to fetch more detailed information about each bookmark instance.
It will look like
{
"count": 6,
"next": null,
"previous": null,
"results": [
{ "content_id": 4
"title": A,
"price": 10$,
"user": 4
},
{
"content_id": 6,
"title": B,
"price": 13$,
"user": 4
},
{
"content_id": 1,
"title": C,
"price": 4$,
"user": 4
},
]
}
I tried many things written in the DRF doc but was not able to find any materials related to my situation.
If you have any idea, please help me.

Answer 1

I think the key you're missing is the source keyword argument for each field. Here's some docs on it for you: http://www.django-rest-framework.org/api-guide/fields/#source
And I believe this implementation should work for you or at least be very close:
class BookmarkSerializer(serializers.ModelSerializer):
content_id = serializers.IntegerField(source='content.id')
title = serializers.CharField(source='content.title')
price = serializers.CharField(source='content.price')
user = serializers.IntegerField(source='user.id')
class Meta:
model = Bookmark
fields = ('content_id', 'user', title', 'price')