Connie's Convenience Store - About Peter Coad

Applying Patterns: Select and Organize Problem-Domain Objects Connie’s Convenience Store 25
A store, as content
Consider a store as content, then as a container.
A store is a part of a chain. “Chain” would be interesting, especially if you wanted
to do a calculation across a collection of stores. Not this time, however.
A store, as a container
A store is a domain-based container.
Think of the store as a large container. What does it contain? Look inside. A store
contains registers, items, cashiers (Figure 1–14).
Store is a domain-based container. Domain-based containers are a convenient place
for expressing responsibilities across a collection of other domain objects, ones that are
not already taken care of by some other collection. Eventually, you may want add to the
kinds of objects that a store object knows.
Figure 1–14: Store–register, item, cashier.
Note that a store object knows its registers, items, and cashiers. That makes sense.
On notation: in each case, the triangle points from a part to a whole.
Transaction–transaction line item
A sale is a transaction.
Nearly all transaction objects have corresponding transaction line items.
Store
n n
Register Item
Cashier
n
1 1
1