Connie's Convenience Store - About Peter Coad

76 Connie’s Convenience Store Working Out Human-Interaction Dynamics with Scenarios
Scenario: make a sale
This scenario consists of a number of shorter scenarios:
– start sale
– sell item
– total the sale
– gets payment by check
– complete the sale.
“Start sale” scenario
Here is the scenario view (Figure 1–51):
SaleWindow
startSale
display
startSale saleWindow.startSale
display
create
create
Figure 1– 51: The “start sale” scenario view.
Note that a sale window knows its corresponding receipt. That’s something new,
something you need to add to the object model.
Note also that basic services (for an object: get, set, add a connection, remove a
connection; for a class: create) appear in scenarios as needed. That’s just fine.
“Sell item” scenario
Here is the scenario view (Figure 1–52):
Sale Receipt
create
addHeadingLine
create
addHeadingLine
Scenario: start sale.
Scenario constraint:
0.1 seconds, 9 out of 10 times,
0.5 seconds max.
Sale.create (session, store; sale)
Receipt.create (sale ; receipt)
receipt.addHeadingLine
saleWindow.display