October 2006
Intermediate to advanced
880 pages
22h 11m
English
Recall the use case we introduced in the previous chapter: An event that triggers the end of an auction has to be processed (Chapter 10, section 10.1, "Transaction essentials"). For the following examples, it doesn't matter who triggered this event; probably an automatic timer ends auctions when their end date and time is reached. It could also be a human operator who triggers the event.
To process the event, you need to execute a sequence of operations: check the winning bid for the auction, charge the cost of the auction, notify the seller and winner, and so on. You could write a single class that has one big procedure. A better design is to move the responsibility for each of these steps into reusable ...