17.5. Object Design: enterItem

The enterItem system operation occurs when a cashier enters the itemID and (optionally) the quantity of something to be purchased. Here is the complete contract:

Contract CO2: enterItem

Operation:enterItem(itemID : ItemID, quantity : integer)
Cross References:

Use Cases: Process Sale

Preconditions:There is an underway sale.
Postconditions:

- A SalesLineItem instance sli was created (instance creation).

- sli was associated with the current Sale (association formed).

- sli.quantity became quantity (attribute modification).

- sli was associated with a ProductSpecification, based on itemID match (association formed).

An interaction diagram will be constructed to satisfy the postconditions of enterItem, using the GRASP patterns ...

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