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:
|Operation:||enterItem(itemID : ItemID, quantity : integer)|
|Preconditions:||There is an underway sale.|
- 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 ...