17.6. Object Design: endSale

The endSale system operation occurs when a cashier presses a button indicating the end of a sale. Here is the contract:

Contract CO3: endSale

Operation:endSale()
Cross References:

Use Cases: Process Sale

Preconditions:There is an underway sale.
Postconditions:Sale.isComplete became true (attribute modification).

Choosing the Controller Class

Our first choice involves handling the responsibility for the system operation message endSale. Based on the Controller GRASP pattern, as for enterItem, we will continue to use Register as a controller.

Setting the Sale.isComplete Attribute

The contract postconditions state:

  • Sale.isComplete became true (attribute modification).

As always, Expert should be the first pattern considered ...

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