網上商店模式(pdf 15頁)(英文)

Solution
Define a catalog class as central point
to collect products. Separate the
different aspects of interest such as
detailed descriptions of products and
related products in distinct classes. Use
an Observer pattern to look for changes
and notify customers of changes.
Solution
The most common metaphor for the shopping
process is based on the concept of shopping
cart, analogous to the carts used in
supermarkets. A customer may have several
shopping carts and each shopping cart will
contain his selections. An order is produced
when the customer decides to buy (checkout)
his cart selections. An invoice is produced for
each order.
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