13. Designing an Address Model

Depending on the merchant’s needs, the business model and the catchment area of the site, the used address models may vary widely. Since django-SHOP allows to subclass almost every database model, addresses are no exception here. The class shop.models.address.BaseAddress only contains a foreign key to the Customer model and a priority field used to sort multiple addresses by relevance.

13.1. Create a Customized Address Model

All the fields which make up an address, such as the addressee, the street name, zip code, etc. are part of the concrete model implementing an address. It is the merchant’s responsibility to define which address fields are required for his needs. Therefore the base address model does not contain any address related fields, they instead have to be declared by the merchant. A concrete implementation of the shipping address model may look like this:

from django.utils.translation import ugettext as _
from shop.models.address import BaseShippingAddress, ISO_3166_CODES

class ShippingAddress(BaseShippingAddress):
    name = models.CharField(_("Full name"), max_length=1024)
    address1 = models.CharField(_("Address line 1"), max_length=1024)
    address2 = models.CharField(_("Address line 2"), max_length=1024)
    zip_code = models.CharField(_("ZIP / Postal code"), max_length=12)
    city = models.CharField(_("City"), max_length=1024)
    country = models.CharField(_("Country"), max_length=3,
                               choices=ISO_3166_CODES)
    class Meta:
        verbose_name = "Shipping Address"
        verbose_name_plural = "Shipping Addresses"

Since the billing address may contain different fields, it must be defined separately from the shipping address. To avoid the duplicate definition of common fields for both models, use a mixin class such as:

from django.db import models
from django.utils.translation import ugettext as _
from shop.models.address import BaseBillingAddress

class AddressModelMixin(models.Model):
    name = models.CharField(_"Full name"), max_length=1024)
    address1 = models.CharField(_"Address line 1"), max_length=1024)
    # other fields

    class Meta:
        abstract = True


class BillingAddress(BaseBillingAddress, AddressModelMixin):
    tax_number = models.CharField("Tax number", max_length=50)

    class Meta:
        verbose_name = _("Billing Address")
        verbose_name_plural = _("Billing Addresses")

13.1.1. The Default Address Model

The simplest way is to materialize the required address classes, is to use them from our default and convenience models: shop.models.defaults.address.ShippingAddress and shop.models.defaults.address.BillingAddress. Before using them, please check if they fulfill your requirements.

13.2. Multiple Addresses

In django-SHOP, if the merchant activates this feature, while setting up the site, customers can register more than one address. Multiple addresses can be activated, when editing the Shipping Address Form Plugin or the Billing Address Form Plugin.

Then during checkout, the customer can select one of a previously entered shipping- and billing addresses, or if he desires add a new one to his list of existing addresses.

13.3. How Addresses are used

Each active Cart object refers to one shipping address object and optionally one billing address object. This means that the customer can change those addresses whenever he uses the supplied address forms.

However, when the customer purchases the content of the cart, that address object is converted into a simple text string and stored inside the then created Order object. This is to freeze the actual wording of the entered address. It also assures that the address used for delivery and printed on the invoice is immune against accidental changes after the purchasing operation.

13.4. Use Shipping Address for Billing

Most customers use their shipping address for billing. Therefore, unless you have really special needs, it is suggested to share all address fields required for shipping, also with the billing address. The customer then can reuse the shipping address for billing, if he desires to. Technically, if the billing address is unset, the shipping address is used anyway, but in django-SHOP the merchant has to actively give permission to his customers, to reuse this address for billing.

The merchant has to actively allow this setting on the site, while editing the Billing Address Form Plugin.

13.5. Address Formatting

Whenever the customer fulfills the purchase operation, the corresponding shipping- and billing address objects are rendered into a short paragraph of plain text, separated by the newline character. This formatted address then is used to print address labels for parcel delivery and printed invoices.

It is the merchant’s responsibility to format these addresses according to the local practice. A customized address template must be added into the merchant’s implementation below the templates folder named myshop/shipping_address.txt or myshop/billing_address.txt. If both address models share the same fields, we may also use myshop/address.txt as a fallback. Such an address template may look like:

myshop/address.txt
{{ address.name }}
{{ address.address1 }}{% if address.address2 %}
{{ address.address2 }}
{% endif %}
{{ address.zip_code }} {{ address.city }}
{{ address.get_country_display }}

This template is used by the method as_text() as found in each address model.

13.6. Address Forms

The address form, where customers can insert their address, is generated automatically and in a DRY manner. This means that whenever a field is added, modified or removed from the address model, the corresponding fields in the address input form, reflect those changes without manual intervention. When creating the form template, we have to write it using the as_div() method. This method also adds automatic client-side form validation to the corresponding HTML code.

13.6.1. Address Form Styling

One problem which remains with automatic form generation, is how to style the input fields. Therefore, django-SHOP wraps every input field into a <div>-element using a CSS class named according to the field. This for instance is useful to shorten some input fields and/or place it onto the same line.

Say, any of our address forms contain the fields zip_code and location as shown in the example above. Then they may be styled as

.shop-address-zip_code {
  width: 35%;
  display: inline-block;
}

.shop-address-city {
  width: 65%;
  display: inline-block;
  margin-left: -4px;
  padding-left: 15px;
}

so that the ZIP field is narrower and precedes the location field on the same line.

13.7. Further Reading

A good introduction on which fields to use where and when in addresses can be found at http://www.uxmatters.com/mt/archives/2008/06/international-address-fields-in-web-forms.php