7.1. Where We Are

Let us look at the classes we have developed so far. Figure 7-1 gives the overall picture, and the listing in Example 7-1 gives the details.

Example 7-1. Class details for the system so far

 class CDRelease     CommonString title     UPCCode upc_code     CDCategory category     Days base_rental_period( )     Dollars get_rental_fee( ) class CDDisc     CDRelease cd_release     PhysicalID physical_id     Rental current_rental     start_rental(Customer the_renter)     end_rental( ) // class PhysicalID class CDCategory class Rental     Customer renter     Timestamp start_time     Timestamp end_time     Days base_rental_period     Boolean is_overdue( ) class CDDiscCollection     CDDisc find_by_physical_id(PhysicalID a_physical_id)     CDDisc [] find_by_cd_release(CDRelease a_cd_release)     // Standard collection operations:     add(CDDisc a_cd_disc)     remove (CDDisc a_cd_disc) class CustomerID class Customer     CustomerID customer_id     CommonString name class CustomerCollection     Customer find_by_customer_id(CustomerID a_customer_id)     // Standard collection operations     add(Customer customer_to_add)     remove(Customer a_customer_id) // Check to see no current rentals 

We have two use cases that we are developing: Checkout_a_CDDisc and Checkin_a_CDDisc . Figure 7-2 gives an overall sequence diagram for the Checkout_a_CDDisc case.

Figure 7-1. Class diagram for the system so far

Figure 7-2. Checkout_a_CDDisc

Likewise, Figure 7-3 gives a sequence diagram for the Checkin_a_CDDisc use case.

Figure 7-3. Checkin_a_CDDisc

For those who prefer pseudocode to document the flow of use cases, the pseudocode for the Checkout_a_CDDisc use case is:

 CDDisc disc_being_rented = CDDiscCollection.find_by_physical_id(physical_id);     Customer renter = CustomerCollection.find_by_customer_id(customer_id);     disc_being_rented.start_rental(renter); 

And for the Checkin_a_CDDisc use case we have:

 CDDisc disc _rented = CDDisc.find_by_physical_id(physical_id);     disc_rented.end_rental( ); 

The find_by... methods for the collections are straightforward, so details are not needed. For CDDisc , the pseudocode for the start_rental( ) and end_rental( ) methods looks like this:

 start_rental(Customer the_renter)         {         if (current_rental != NULL)             signal CDDiscAlreadyRented;         current_rental = new Rental(the_renter);         produce_contract( );         }     end_rental( )         {         if (current_rental.is_overdue( ))             perform_late_rental_procedure( );         current_rental = NULL;         } 

We still have two operations that we have not examined in any detail: produce_contract( ) and perform_late_rental_procedure( ) . We look at those next .