Quantity / Tiered / Volume Pricing code!

[Nick Albright]

I saw a few questions in here on volume pricing, but didn't see any solutions.  We just came up with one, so I thought I'd share.  Pretty much you need to mod 3 places.  The StockRecord model (add a quantity field), the Strategy for selecting a stock record, and lastly the logic for adding to the cart.  The latter is the big change, as we are just changing 1 line in the middle of it, so end up copy/pasting the whole function.

The stock record, to add quantity

# store/partner/models.py

from django.db import models

from oscar.apps.partner.abstract_models import AbstractStockRecord

class StockRecord( AbstractStockRecord ):

        quantity = models.IntegerField( db_index = True,

                                    default = 1,

                                    help_text = 'Min quantity to get the price')

    class Meta( AbstractStockRecord.Meta ):

        unique_together = ( 'product', 'partner', 'quantity' )

        index_together = ['product', 'quantity']

 

The strategy, to get passed in quantity, and select based on qty

# store/partner/strategy.py

from oscar.apps.partner.strategy import DeferredTax, StockRequired, Structured, PurchaseInfo

from store.partner.models import StockRecord

from decimal import Decimal as D

class UseQuantityStockRecord( object ):

    def fetch_for_line( self, line, stockrecord = None ):

        """

        Overrideen oscar's app/partner/strategy.py Base's method, to use qty

        """

        # Added quantity arg for quantity pricing

        return( self.fetch_for_product(line.product, quantity = line.quantity))

    def fetch_for_product(self, product, stockrecord=None, quantity=1):

        """

        Overrideen oscar's app/partner/strategy.py Structures's method, to use qty

        """

        if stockrecord is None:

            stockrecord = self.select_stockrecord(product, quantity=quantity)

        return PurchaseInfo(

            price=self.pricing_policy(product, stockrecord),

            availability=self.availability_policy(product, stockrecord),

            stockrecord=stockrecord)

    def select_stockrecord( self, product, quantity=1 ):

        try:

            return( product.stockrecords.filter( quantity__lte = quantity

                                             ).order_by('-quantity')[0])

        except (StockRecord.DoesNotExist, IndexError):
            return( None )

And the ugly cut and paste to just change 1 line essentially/the add to basket logic. :)

Enter code here...# store/basket/models.py

from oscar.apps.basket.abstract_models import AbstractBasket

class Basket( AbstractBasket ):

    """

    Needed to allow us to do quantity pricing for adding to the basket.

    We only change like 4 lines in the middle of add_product

    """

    def add_product(self, product, quantity=1, options=None):

        """

        Add a product to the basket

        'stock_info' is the price and availability data returned from

        a partner strategy class.

        The 'options' list should contains dicts with keys 'option' and 'value'

        which link the relevant product.Option model and string value

        respectively.

        Returns (line, created).

          line: the matching basket line

          created: whether the line was created or updated

        """

        if options is None:

            options = []

        if not self.id:

            self.save()

        # Ensure that all lines are the same currency

        price_currency = self.currency

        # BEGIN - Edits for quantity pricing

        try:

            stock_info = self.strategy.fetch_for_product(product, quantity=quantity)

        except TypeError: # Backwards compatibility!

            stock_info = self.strategy.fetch_for_product(product)

        # END - Edits for quantity pricing

        if price_currency and stock_info.price.currency != price_currency:

            raise ValueError((

                "Basket lines must all have the same currency. Proposed "

                "line has currency %s, while basket has currency %s")

                % (stock_info.price.currency, price_currency))

        if stock_info.stockrecord is None:

            raise ValueError((

                "Basket lines must all have stock records. Strategy hasn't "

                "found any stock record for product %s") % product)

        # Line reference is used to distinguish between variations of the same

        # product (eg T-shirts with different personalisations)

        line_ref = self._create_line_reference(

            product, stock_info.stockrecord, options)

        # Determine price to store (if one exists).  It is only stored for

        # audit and sometimes caching.

        defaults = {

            'quantity': quantity,

            'price_excl_tax': stock_info.price.excl_tax,

            'price_currency': stock_info.price.currency,

        }

        if stock_info.price.is_tax_known:

            defaults['price_incl_tax'] = stock_info.price.incl_tax

        # raise Exception( str( defaults ))

        line, created = self.lines.get_or_create(

            line_reference=line_ref,

            product=product,

            stockrecord=stock_info.stockrecord,

            defaults=defaults)

        if created:

            for option_dict in options:

                line.attributes.create(option=option_dict['option'],

                                       value=option_dict['value'])

        else:

            line.quantity += quantity

            line.save()

        self.reset_offer_applications()

        # Returning the line is useful when overriding this method.

        return line, created

    add_product.alters_data = True

    add = add_product

from oscar.apps.basket.models import *  # noqa

I hope this helps others looking to do the same!