Brass * p_clients[CLIENTS];
std::string temp;
long tempnum;
double tempbal;
char kind;
for (int i = 0; i < CLIENTS; i++)
{
cout << "Enter client's name: ";
getline(cin,temp);
cout << "Enter client's account number: ";
cin >> tempnum;
cout << "Enter opening balance: $";
cin >> tempbal;
cout << "Enter 1 for Brass Account or "
<< "2 for BrassPlus Account: ";
while (cin >> kind && (kind != '1' && kind != '2'))
cout <<"Enter either 1 or 2: ";
if (kind == '1')
p_clients[i] = new Brass(temp, tempnum, tempbal);
else
{
double tmax, trate;
cout << "Enter the overdraft limit: $";
cin >> tmax;
cout << "Enter the interest rate "
<< "as a decimal fraction: ";
cin >> trate;
p_clients[i] = new BrassPlus(temp, tempnum, tempbal,
tmax, trate);
}
while (cin.get() != '\n')
continue;
}
cout << endl;
for (int i = 0; i < CLIENTS; i++)
{
p_clients[i]->ViewAcct();
cout << endl;
}
for (int i = 0; i < CLIENTS; i++)
{
delete p_clients[i]; // free memory
}
cout << "Done.\n";
return 0;
}
The program in Listing 13.10 lets user input determine the type of account to be added and then uses new to create and initialize an object of the proper type. You may recall that getline(cin,temp) reads a line of input from cin and stores it in the string object temp.
Here is a sample run of the program in Listing 13.10:
Enter client's name: Harry Fishsong
Enter client's account number: 112233
Enter opening balance: $1500
Enter 1 for Brass Account or 2 for BrassPlus Account: 1
Enter client's name: Dinah Otternoe
Enter client's account number: 121213
Enter opening balance: $1800
Enter 1 for Brass Account or 2 for BrassPlus Account: 2
Enter the overdraft limit: $350
Enter the interest rate as a decimal fraction: 0.12
Enter client's name: Brenda Birdherd
Enter client's account number: 212118
Enter opening balance: $5200
Enter 1 for Brass Account or 2 for BrassPlus Account: 2
Enter the overdraft limit: $800
Enter the interest rate as a decimal fraction: 0.10
Enter client's name: Tim Turtletop
Enter client's account number: 233255
Enter opening balance: $688
Enter 1 for Brass Account or 2 for BrassPlus Account: 1
Client: Harry Fishsong
Account Number: 112233
Balance: $1500.00
Client: Dinah Otternoe
Account Number: 121213
Balance: $1800.00
Maximum loan: $350.00
Owed to bank: $0.00
Loan Rate: 12.00%
Client: Brenda Birdherd
Account Number: 212118
Balance: $5200.00
Maximum loan: $800.00
Owed to bank: $0.00
Loan Rate: 10.00%
Client: Tim Turtletop
Account Number: 233255
Balance: $688.00
Done.
The polymorphic aspect is provided by the following code:
for (i = 0; i < CLIENTS; i++)
{
p_clients[i]->ViewAcct();
cout << endl;
}
If the array member points to a Brass object, Brass::ViewAcct() is invoked; if the array member points to a BrassPlus object, BrassPlus::ViewAcct() is invoked. If Brass::ViewAcct() were been declared as virtual, Brass:ViewAcct() would be invoked in all cases.
The Need for Virtual Destructors
The code in Listing 13.10 that uses delete to free the objects allocated by new illustrates why the base class should have a virtual destructor, even if no destructor appears to be needed. If the destructors are not virtual, then just the destructor corresponding to the pointer type is called. In Listing 13.10, this means that only the Brass destructor would be called, even if the pointer pointed to a BrassPlus object. If the destructors are virtual, the destructor corresponding to the object type is called. So if a pointer points to a BrassPlus object, the BrassPlus destructor is called. And when a BrassPlus destructor finishes, it automatically calls the base-class constructor. Thus, using virtual destructors ensures that the correct sequence of destructors is called. In Listing 13.10, this correct behavior isn’t essential because the destructors do nothing. But if, say, BrassPlus had a do-something destructor, it would be vital for Brass to have a virtual destructor, even if it did nothing.
Static and Dynamic Binding
