5. Catalog

The catalog probably is that part, where customers of our e-commerce site spend the most time. Often it even makes sense, to start the Catalog List View on the main landing page.

In this documentation we presume that categories of products are built up using specially tagged CMS pages in combination with a djangoCMS apphook. This works perfectly well for most implementation, but some sites may require categories implemented independently of the CMS.

Using an external djangoSHOP plugin for managing categories is a very conceivable solution, and we will see separate implementations for this feature request. Using such an external category plugin can make sense, if this e-commerce site requires hundreds of hierarchical levels and/or these categories require a set of attributes which are not available in CMS pages. If you are going to use externally implemented categories, please refer to their documentation, since here we proceed using CMS pages as categories.

A nice aspect of djangoSHOP is, that it doesn’t require the programmer to write any special Django Views in order to render the catalog. Instead all merchant dependent business logic goes into a serializer, which in this documentation is referred as ProductSummarySerializer.

5.1. Catalog List View

In this documentation, the catalog list view is implemented as a djangoCMS page. Depending on whether the e-commerce aspect of that site is the most prominent part, or just a niche of the CMS select an appropriate location in the page tree and create a new page. This will become the root of our catalog list.

But first we must Create the ProductsListApp.

5.1.1. Create the ProductsListApp

To retrieve a list of product models, the Catalog List View requires a djangoCMS apphook. This ProductsListApp must be added into a file named cms_app.py and located in the root folder of the merchant’s project:

myshop/cms_app.py

from cms.app_base import CMSApp
from cms.apphook_pool import apphook_pool

class ProductsListApp(CMSApp):
    name = _("Catalog List")
    urls = ['myshop.urls.products']

apphook_pool.register(ProductsListApp)

as all apphooks, it requires a file defining its urlpatterns:

myshop/urls/products.py

from django.conf.urls import patterns, url
from rest_framework.settings import api_settings
from shop.views.catalog import CMSPageProductListView
from myshop.serializers import ProductSummarySerializer

urlpatterns = patterns('',
    url(r'^$', CMSPageProductListView.as_view(
        serializer_class=ProductSummarySerializer,
    )),
    # other patterns
)

Here the ProductSummarySerializer serializes the product models into a representation suitable for being rendered inside a CMS page, as well as being converted to JSON. This allows us to reuse the same Django View (CMSPageProductListView) whenever the catalog list switches into infinite scroll mode, where it only requires the product’s summary digested as JavaScript objects.

In case we need Additional Product Serializer Fields, lets add them to this class using the serializer fields from the Django RESTFramework library.

5.1.2. Add the Catalog to the CMS

In the page list editor of djangoCMS, create a new page at an appropriate location of the page tree. As the page title and slug we should use something describing our product catalog in a way, both meaningful to the customers as well as to search engines.

Next, we change into advanced setting.

As a template we use one with a big placeholder, since it must display our list of products.

As Application, select “Catalog List” or whatever we named our ProductsListApp. This selects the apphook we created in the previous section.

Then we save the page, change into Structure mode and locate the Main Content Container. Here we add a container with a Row and Column. As the child of this column we chose a Catalog List View plugin from section Shop.

Finally we publish the page and enter some text into the search field. Since we haven’t assigned any products to the CMS page, we won’t see anything yet.

5.2. Catalog Detail View

The product’s detail pages are the only ones not being managed by the CMS. This is because we often have thousands of products and creating a CMS page for each of them, would be kind of overkill.

Therefore the template used to render the products’s detail view is selected automatically by the ProductRetrieveView [1] following these rules:

• look for a template named <myshop>/catalog/<product-model-name>-detail.html [2] [3], otherwise
• look for a template named <myshop>/catalog/product-detail.html [2], otherwise
• use the template shop/catalog/product-detail.html.

[1]	This is the View class responsible for rendering the product’s detail view.

[2]	(1, 2) <myshop> is the app label of the project in lowercase.

[3]	<product-model-name> is the class name of the product model in lowercase.

5.2.1. Use CMS Placeholders on Detail View

If we require CMS functionality for each product’s detail page, its quite simple to achieve. To the model class implementing our Product, add djangoCMS Placeholder field named placeholder.Then add the templatetag {% render_placeholder product.placeholder %} the the template implementing the detail view of our product.

5.2.2. Route requests on Detail View

The ProductsListApp, which we previously have registered into djangoCMS, is able to route requests on all of its sub-URLs. This is done by expanding the current list of urlpatterns:

myshop/urls/products.py

from django.conf.urls import patterns, url
from shop.views.catalog import ProductRetrieveView
from myshop.serializers import ProductDetailSerializer

urlpatterns = patterns('',
    # previous patterns
    url(r'^(?P<slug>[\w-]+)$', ProductRetrieveView.as_view(
        serializer_class=ProductDetailSerializer,
    )),
    # other patterns
)

All business logic regarding our product now goes into our customized serializer class named ProductDetailSerializer. This class then may access the various attributes of our product model and merge them into a serializable representation.

This serialized representation normally requires all attributes from our model, therefore we can write it as simple as:

from shop.rest.serializers import ProductDetailSerializerBase

class ProductDetailSerializer(ProductDetailSerializerBase):
    class Meta:
        model = Product
        exclude = ('active',)

In case we need Additional Product Serializer Fields, lets add them to this class using the serializer fields from the Django RESTFramework library.

5.2.2.1. Additional Product Serializer Fields

Sometimes such a serializer field shall return a HTML snippet; this for instance is required for image source (<img src="..." />) tags, which must thumbnailed by the server when rendered using the appropriate templatetags from the easythumbnail library. For these use cases add a field of type foo = SerializerMethodField() with an appropriate method get_foo() to our serializer class. This method then may forward the given product to a the built-in renderer:

class ProductDetailSerializer(ProductDetailSerializerBase):
    # other attributes

    def get_foo(self, product):
        return self.render_html(product, 'foo')

This HTML renderer method looks up for a template following these rules:

• look for a template named <myshop>/product/catalog-<product-model-name>-<second-argument>.html [4] [5] [6], otherwise
• look for a template named <myshop>/product/catalog-product-<second-argument>.html [4] [6], otherwise
• use the template shop/product/catalog-product-<second-argument>.html [6].

[4]	(1, 2) <myshop> is the app label of the project in lowercase.

[5]	<product-model-name> is the class name of the product model in lowercase.

[6]	(1, 2, 3) <field-name> is the attribute name of the just declared field in lowercase.

5.2.3. Emulate Categories

Since we want to use CMS pages to emulate categories, the product model must declare a relationship between the CMS pages and itself. This usually is done by adding a Many-to-Many field named cms_pages to our Product model.

Since we work with deferred models, we can not use the mapping table, which normally is generated automatically for Many-to-Many fields by the Django framework. Instead, this mapping table must be created manually and referenced using the though parameter, when declaring the field:

from shop.models.product import BaseProductManager, BaseProduct
from shop.models.related import BaseProductPage

class ProductPage(BaseProductPage):
    """Materialize many-to-many relation with CMS pages"""

class Product(BaseProduct):
    # other model fields
    cms_pages = models.ManyToManyField('cms.Page',
        through=ProductPage)

    objects = ProductManager()

In this example the class ProductPage is responsible for storing the mapping information between our Product objects and the CMS pages.

5.2.3.1. Admin Integration

To simplify the declaration of the admin backend used to manage our Product model, djangoSHOP is shipped with a special mixin class, which shall be added to the product’s admin class:

from django.contrib import admin
from shop.admin.product import CMSPageAsCategoryMixin
from myshop.models import Product

@admin.register(Product)
class ProductAdmin(CMSPageAsCategoryMixin, admin.ModelAdmin):
    fields = ('product_name', 'slug', 'product_code',
        'unit_price', 'active', 'description',)
    # other admin declarations

This then adds a horizontal filter widget to the product models. Here the merchant must select each CMS page, where the currently edited product shall appear on.

If we are using the method render_html() to render HTML snippets, these are cached by djangoSHOP, if caching is configured and enabled for that project. Caching these snippets is highly recommended and gives a noticeable performance boost, specially while rendering catalog list views.

Since we would have to wait until they expire naturally by reaching their expire time, djangoSHOP offers a mixin class to be added to the Product admin class, to expire all HTML snippets of a product altogether, whenever a product in saved in the backend. Simply add shop.admin.product.InvalidateProductCacheMixin to the ProductAdmin class described above.

Note

Due to the way keys are handled in many caching systems, the InvalidateProductCacheMixin only makes sense if used in combination with the redis_cache backend.