13.2. Example Contract: enterItem

Before examining the reason to write a contract, an example is worthwhile. The following describes a contract for the enterItem system operation.

Contract CO2: enterItem

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

Use Cases: Process Sale

Preconditions:There is a sale underway.
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).

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