17.4. Object Design: makeNewSale

The makeNewSale system operation occurs when a cashier requests to start a new sale, after a customer has arrived with things to buy. The use case may have been sufficient to decide what was necessary, but for this case study we wrote contracts for all the system events, for explanation and completeness.

Contract CO1: makeNewSale

Operation:makeNewSale()
Cross References:

Use Cases: Process Sale

Preconditions:None
Postconditions:

- A Sale instance s was created (instance creation).

- s was associated with the Register (association formed).

- Attributes of s were initialized.

Choosing the Controller Class

Our first design choice involves choosing the controller for the system operation message enterItem. By the Controller ...

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