Extending Calculators

You can extend any of the pricing calculators to add functionality, if that suits your needs more than implementing one of the provided interfaces. As an example this section describes the order of calls in ItemDiscountCalculator; other calculators may vary:

  1. The priceItems method changes the price of input items. It first calls findQualifyingItems to get items whose prices need changing. It then calls priceQualifyingItems to change their price.

  2. The findQualifyingItems method selects items to be discounted. It bases item selection on attributes of the input environment as represented by the method’s parameters.

  3. The priceQualifyingItems method modifies the prices of an input collection of items. It also verifies that the items’ audit trail is maintained. priceQualifyingItems calls priceQualifyingItem once for each input item to be priced.

  4. The priceQualifyingItem method modifies the price of the input item. It also verifies that the item’s audit trail is maintained. priceQualifyingItem calls each priceDetailedItemPriceInfo, discounting details until the total number of items to discount has been reached.

  5. The priceDetailedItemPriceInfo method modifies the price of a detailedItemPriceInfo. It maintains the audit trail and marks the details that have acted as qualifiers. It calls findAdjustedPrice to find the new price of the details.

  6. The findAdjustedPrice method produces a number that is the new price of a DetailedItemPriceInfo. It examines the existing price and the input parameters, and it returns the new price.

You can override any of these methods to provide new functionality while leveraging the existing code.