Database Reference
In-Depth Information
Note that we're including
items.sku
in our update spec. This allows us to use the
positional
$
in our
$set
modifier to update the correct (matching) line item.
Both here and in the rollback operation, we're using the
$inc
modifier rather than
$set
to update the quantity. This allows us to correctly handle situations where a
user might be updating the cart multiple times simultaneously (say, in two different
browser windows).
Here again, we're using the positional
$
in our update to
carted
, so we need to in-
clude the
cart_id
in our update spec.
Once again, we're using
_id
in all our updates, so adding an index doesn't help us here.
Checking out
The checkout operation needs to do two main operations:
▪ Capture payment details.
▪ Update the
carted
items once payment is made.
Our basic algorithm here is as follows:
1. Lock the cart by setting it to
pending
status.
2. Collect payment for the cart. If this fails, unlock the cart by setting it back to
active
status.
3. Set the cart's status to
complete
.
4. Remove all references to this cart from any
carted
properties in the
product
collec-
tion.
The code would look something like the following:
def
def
checkout
(
cart_id
):
now
=
datetime
.
utcnow
()
result
=
db
.
cart
.
update
(
{
'_id'
:
cart_id
,
'status'
:
'active'
},
