Connie's Convenience Store - About Peter Coad

Establishing Responsibilities for Problem-Domain Objects Connie’s Convenience Store 45
Register
Establish responsibilities: “what I know.”
What does a register object know? It knows its:
– number (e.g., register number 2).
Establish responsibilities: “who I know.”
Who does a register object know? It knows its:
– store (one)
– session (zero or more)
– cash drawer (one, in this system).
(From the other direction, each session, and cash drawer knows its register. A store
knows its registers, too.)
Establish responsibilities: “what I do.”
What does a register object do?
It provides basic services (get, set, add, remove, delete).
What else could it do?
A register object knows its session objects. So it could do something across that
collection of objects, something like this:
– how much (money collected) over interval
– how many (sales) over interval.
Add register responsibilities to the model (Figure 1–29):
Session
Store
Register
1 n
number
howManyOverInterval
howMuchOverInterval
1 1
Figure 1–29: Register: “what I know; who I know; what I do.”
n
1
CashDrawer