Displaying Django subcategories in category and products in each category json as Json Child

Question

Hi in my Django oscar project which Implements Django oscar. I am able to implement my custom API which I use to view categories and display them. The issue with the API now is that subcategories of a category appear in my API view as categories and I would like them to be in an array indicating that they are subcategories. My categories code is as follows

customapi serializer class

class CategorySerializer(serializers.ModelSerializer):
    class Meta:
        model = Category
        fields = ('id', 'numchild', 'name', 'description', 'image', 'slug')

Views

class CategoryList(generics.ListAPIView):
    queryset = Category.objects.all()
    serializer_class = CategorySerializer


class CategoryDetail(generics.RetrieveAPIView):
    queryset = Category.objects.all()
    serializer_class = CategorySerializer

customapi/urls.py

url(r'^caty/$', CategoryList.as_view(), name='category-list'),
url(r'^caty/(?P<category_slug>[\w-]+(/[\w-]+)*)_(?P<pk>\d+)/$',
        CategoryDetail.as_view(), name='category'),

Json

[
    {
        "id": 2,
        "path": "0001",
        "depth": 1,
        "numchild": 4,
        "name": "Clothes",
        "description": "<p>Beautiful Clothes</p>",
        "image": null,
        "slug": "clothes"
    },
    {
        "id": 8,
        "path": "00010001",
        "depth": 2,
        "numchild": 0,
        "name": "c",
        "description": "",
        "image": null,
        "slug": "c"
    },
    {
        "id": 7,
        "path": "00010002",
        "depth": 2,
        "numchild": 0,
        "name": "b",
        "description": "",
        "image": null,
        "slug": "b"
    },
    {
        "id": 6,
        "path": "00010003",
        "depth": 2,
        "numchild": 0,
        "name": "a",
        "description": "",
        "image": null,
        "slug": "a"
    },
    {
        "id": 5,
        "path": "00010004",
        "depth": 2,
        "numchild": 0,
        "name": "MsWears",
        "description": "",
        "image": null,
        "slug": "mswears"
    },]

notice the numchild is 4 for the first which signifies it is the parent category and the rest are the subcategories.

The subcategories are rendered like this from the Django-oscar model

class AbstractCategory(MP_Node):
    """
    A product category. Merely used for navigational purposes; has no effects on business logic.

    Uses Django-treebeard.
    """
    name = models.CharField(_('Name'), max_length=255, db_index=True)
    description = models.TextField(_('Description'), blank=True)
    image = models.ImageField(_('Image'), upload_to='categories', blank=True,
                              null=True, max_length=255)
    slug = SlugField(_('Slug'), max_length=255, db_index=True)

    _slug_separator = '/'
    _full_name_separator = ' > '

    def __str__(self):
        return self.full_name

    @property
    def full_name(self):
        """
        Returns a string representation of the category and it's ancestors,
        e.g. 'Books > Non-fiction > Essential programming'.

        It's rarely used in Oscar's codebase, but used to be stored as a
        CharField and is hence kept for backward compatibility. It's also sufficiently useful to keep around.
        """
        names = [category.name for category in self.get_ancestors_and_self()]
        return self._full_name_separator.join(names)

    @property
    def full_slug(self):
        """
        Returns a string of this category's slug concatenated with the slugs
        of it's ancestors, e.g. 'books/non-fiction/essential-programming'.

        Oscar used to store this as in the 'slug' model field, but this field
        has been re-purposed to only store this category's slug and to not
        include it's ancestors' slugs.
        """
        slugs = [category.slug for category in self.get_ancestors_and_self()]
        return self._slug_separator.join(slugs)

    def generate_slug(self):
        """
        Generates a slug for a category. This makes no attempt at generating a unique slug.
        """
        return slugify(self.name)

    def ensure_slug_uniqueness(self):
        """
        Ensures that the category's slug is unique amongst its siblings.
        This is inefficient and probably not thread-safe.
        """
        unique_slug = self.slug
        siblings = self.get_siblings().exclude(pk=self.pk)
        next_num = 2
        while siblings.filter(slug=unique_slug).exists():
            unique_slug = '{slug}_{end}'.format(slug=self.slug, end=next_num)
            next_num += 1

        if unique_slug != self.slug:
            self.slug = unique_slug
            self.save()

    def save(self, *args, **kwargs):
        """
        Oscar traditionally auto-generated slugs from names. As that is often convenient, we still do so if a slug is not supplied through other means. If you want to control slug creation, just create instances with a slug already set, or expose a field on the appropriate forms.
        """
        if self.slug:
            # Slug was supplied. Hands off!
            super(AbstractCategory, self).save(*args, **kwargs)
        else:
            self.slug = self.generate_slug()
            super(AbstractCategory, self).save(*args, **kwargs)
            # We auto-generated a slug, so we need to make sure that it's
            # unique. As we need to be able to inspect the category's siblings
            # for that, we need to wait until the instance is saved. We
            # update the slug and save again if necessary.
            self.ensure_slug_uniqueness()

    def get_ancestors_and_self(self):
        """
        Gets ancestors and includes itself. Use treebeard's get_ancestors
        if you don't want to include the category itself. It's a separate function as it's commonly used in templates.
        """
        return list(self.get_ancestors()) + [self]

    def get_descendants_and_self(self):
        """
        Gets descendants and includes itself. Use treebeard's get_descendants
        if you don't want to include the category itself. It's a separate function as it's commonly used in templates.
        """
        return list(self.get_descendants()) + [self]

    def get_absolute_url(self):
        """
        Our URL scheme means we have to look up the category's ancestors. As that is a bit more expensive, we cache the generated URL. That is
        safe even for a stale cache, as the default implementation of
        ProductCategoryView does the lookup via primary key anyway. But if you change that logic, you'll have to reconsider the caching approach.
        """
        current_locale = get_language()
        cache_key = 'CATEGORY_URL_%s_%s' % (current_locale, self.pk)
        url = cache.get(cache_key)
        if not url:
            url = reverse(
                'catalogue:category',
                kwargs={'category_slug': self.full_slug, 'pk': self.pk})
            cache.set(cache_key, url)
        return url

    class Meta:
        abstract = True
        app_label = 'catalogue'
        ordering = ['path']
        verbose_name = _('Category')
        verbose_name_plural = _('Categories')

    def has_children(self):
        return self.get_num_children() > 0

    def get_num_children(self):
        return self.get_children().count() 

when a category is selected, the corresponding JSON so look like this

 {
        "url": "http://127.0.0.1:8000/nativapi/products/16/",
        "id": 16,
        "title": "Deall",
        "images": [],
        "price": {
            "currency": "NGN",
            "excl_tax": "1000.00",
            "incl_tax": "1000.00",
            "tax": "0.00"
        },
        "availability": "http://127.0.0.1:8000/nativapi/products/16/availability/"
    },
    {
        "url": "http://127.0.0.1:8000/nativapi/products/13/",
        "id": 13,
        "title": "ada",
        "images": [
            {
                "id": 8,
                "original": "http://127.0.0.1:8000/media/images/products/2018/05/f3.jpg",
                "caption": "",
                "display_order": 0,
                "date_created": "2018-05-26T17:24:34.762848Z",
                "product": 13
            },]

this means that only the products under that category are returned. and if a category has a number if a child, the number of the child should be returned in as an object Array.

Answer 1

I would suggest keeping category specific data separate (in details page) and only having a products API.

For getting products under a certain category, you could do something like -

views.py

from django.shortcuts import get_object_or_404
from oscar.core.loading import get_model
from rest_framework import generics
from oscarapi.serializers import ProductsSerializer


Category = get_model('catalogue', 'Category')
Product = get_model('catalogue', 'Product')


class CategoryProductsView(generics.ListAPIView):
    serializer_class = ProductsSerializer

    def get_queryset(self):
        cat_id = self.kwargs.get('pk', None)
        if cat_id is not None:
            category = get_object_or_404(Category, id=cat_id)
            return Product.objects.filter(
                categories__path__startswith=category.path).all()
        else:
            return Product.objects.none()

urls.py

from views import CategoryProductsView

urlpatterns = [
    ...
    url(r'^caty/(?P<pk>[0-9]+)/products/$', CategoryProducts.as_view(), name='category-products'),
    ...
]

Since we are using categories__path__startswith we'd get all products under that category, including those under the subcategory of given category, and so on.

Update

As for the subcategories you want listed, you could simply add a SerializerMethodField() to do that for you. I'd suggest getting a list of ids for the subcategories so that further fetching the details of that subcategory would be easier given it's id (simple lookup from the existing list of categories)

serializers.py

from oscarapi.utils import OscarModelSerializer
from rest_framework import serializers


class CategorySerializer(OscarModelSerializer):
    subcategories = serializers.SerializerMethodField()

    class Meta:
        model = Category
        fields = ('id', 'numchild', 'name', 'description', 'image', 'slug',
                  'path', 'depth', 'subcategories')

    def get_subcategories(self, obj):
        return Category.objects.filter(path__startswith=obj.path,
                                       depth=obj.depth+1
                              ).values_list('id', flat=True)

sample output

"results": [
    {
        "id": 1,
        "numchild": 1,
        "name": "Cat1",
        "description": "",
        "image": "http://localhost:8001/media/categories/images/categories/cat1.jpg",
        "slug": "cat1",
        "path": "0001",
        "depth": 1,
        "subcategories": [
            2
        ]
    },
    {
        "id": 2,
        "numchild": 0,
        "name": "SubCat1",
        "description": "",
        "image": null,
        "slug": "subcat1",
        "path": "00010001",
        "depth": 2,
        "subcategories": [
        ]
    },
]

Answer 2

django-oscar uses django-treebeard for a materialized path implementation, pretty much the opposite of the nested hierarchy you want to retrieve.

I have no experience in writing serializers along with treebeard, but i am pretty sure that you will need to rewrite your Serializer to something like

# Get all categories from /caty
class CategorySerializer(serializers.ModelSerializer):
    children = serializers.SerializerMethodField('get_children')

    def get_children(self, obj):
        if obj.numchild == 0:
            return None
        # Use treebeards built-in tree generation
        [CategorySerializer(child) for child in Category.get_tree(obj)]

    class Meta:
        model = Category

Notice that i have NOT tested any of this, i am just trying to point you in a direction that might bring you closer to a solution.