django admin foreign key default value inline - django

Question

I'm converting an ancient Client/Server app (Delphi) into a Django app for a small brick and morter bookstore (wife's).
Since most functions are admin, I'm using the Django admin interface with grappelli for some easier lookups.
I have 3 models: Book, Sale and Item.
class Book(TimeStampedModel):
"""
Books are described individually and are related to collections
as many to many. Every book in this system is unique - i.e. there are
not quantity fields. This is optimized for used book stores where book
condition is essential.
"""
STATUS_CHOICES = (
('IN STOCK', 'IN STOCK'),
('SOLD', 'SOLD'),
('ON LOAN', 'ON LOAN'),
('HOLD', 'HOLD'),
)
isbn = models.CharField(max_length=50, blank=True)
title = models.CharField(max_length=200, blank=False, db_index=True)
author = models.CharField(max_length=200, blank=True)
sell_price = models.DecimalField(max_digits=10,decimal_places=2, default=0)
description = models.TextField()
collections = models.ManyToManyField(Collection)
class Meta:
index_together = [
["author", "title"],
["status", "title", "author"],
]
def __unicode__(self):
return "%s [%d] - %s - $%.2f" % (self.title, self.id, self.book_type, self.sell_price)
#staticmethod
def autocomplete_queryset():
instock = Book.objects.filter(status="IN STOCK")
return instock
#staticmethod
def autocomplete_search_fields():
return("id__iexact", "title__istartswith",)
class Sale(TimeStampedModel):
"""
Sales group all sold items which may or may not be books and are sold to contacts.
We use a "generic" contact of "cash" for non named contacts
"""
PAYMENT_TYPE_CHOICES = ( ('Cash', 'Cash'), ('Charge', 'Charge'), ('Check', 'Check'))
contact = models.ForeignKey(Contact, null=True)
sale_date = models.DateField(blank=True,default=datetime.date.today, db_index=True)
payment_type = models.CharField(max_length=50, choices=PAYMENT_TYPE_CHOICES)
taxed = models.BooleanField(default=True)
tax_exempt_no = models.CharField(blank=True, max_length=50)
sales_tax = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)
amt_tender = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)
pct_discount = models.SmallIntegerField(blank=True, null=True)
amt_credit = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)
amt_shipping = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)
amt_due = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)
tot_sale = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)
tot_items = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)
ordering = ['-sale_date']
def __unicode__(self):
return str(self.sale_date)
class Item(TimeStampedModel):
"""
Items are usually books sold on a sale. Items can also be entered manually
at time of sale if they are not books from inventory
"""
sale = models.ForeignKey(Sale)
book = models.ForeignKey(Book, null=True, blank=True)
item_desc = models.CharField(blank=True, max_length=200)
cost = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)
sell_price = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)
def __unicode__(self):
return self.item_desc
For the Sale form, I use an admin form with Tabular inline Items. Items are usually books (via a foreign key lookup), but can also be entered manually for non-inventory items so I have a sell_price both in the book model and in the item model.
class ItemInline(admin.TabularInline):
model = Item
raw_id_fields = ("book",)
autocomplete_lookup_fields = {
'fk': ['book'],
}
extra = 2
What I'd like to do in the foreign key lookup is to return the key of the book AND fill in the Item's sellprice with the sellprice from the book I looked up.
I have the basic lookup working just fine but can't find out how to set the item sellprice to the book's sellprice immediately after the lookup.
Any advice is appreciated! I have tried figuring out the objects to put some JS logic in but the inlines get object ids created dynamically, I think. I'm no JS expert.