Creating an inheritance hierarchy – bank accounts

(Account Inheritance Hierarchy) Create an inheritance hierarchy that a bank might use to
represent customers’ bank accounts. All customers at this bank can deposit (i.e., credit) money into
their accounts and withdraw (i.e., debit) money from their accounts. More specific types of accounts
also exist. Savings accounts, for instance, earn interest on the money they hold. Checking accounts,
on the other hand, charge a fee per transaction (i.e., credit or debit).
Create an inheritance hierarchy containing base class Account and derived classes Savings-
Account and CheckingAccount that inherit from class Account. Base class Account should include
one data member of type double to represent the account balance. The class should provide a constructor
that receives an initial balance and uses it to initialize the data member. The constructor
should validate the initial balance to ensure that it’s greater than or equal to 0.0. If not, the balance
should be set to 0.0 and the constructor should display an error message, indicating that the initial
balance was invalid. The class should provide three member functions. Member function credit

should add an amount to the current balance. Member function debit should withdraw money
from the Account and ensure that the debit amount does not exceed the Account’s balance. If it
does, the balance should be left unchanged and the function should print the message “Debit
amount exceeded account balance.” Member function getBalance should return the current
balance.
Derived class SavingsAccount should inherit the functionality of an Account, but also include
a data member of type double indicating the interest rate (percentage) assigned to the Account.
SavingsAccount’s constructor should receive the initial balance, as well as an initial value for the
SavingsAccount’s interest rate. SavingsAccount should provide a public member function
calculateInterest that returns a double indicating the amount of interest earned by an account.
Member function calculateInterest should determine this amount by multiplying the interest
rate by the account balance. [Note: SavingsAccount should inherit member functions credit and
debit as is without redefining them.]
Derived class CheckingAccount should inherit from base class Account and include an additional
data member of type double that represents the fee charged per transaction. Checking-
Account’s constructor should receive the initial balance, as well as a parameter indicating a fee
amount. Class CheckingAccount should redefine member functions credit and debit so that they
subtract the fee from the account balance whenever either transaction is performed successfully.
CheckingAccount’s versions of these functions should invoke the base-class Account version to perform
the updates to an account balance. CheckingAccount’s debit function should charge a fee
only if money is actually withdrawn (i.e., the debit amount does not exceed the account balance).
[Hint: Define Account’s debit function so that it returns a bool indicating whether money was
withdrawn. Then use the return value to determine whether a fee should be charged.]
After defining the classes in this hierarchy, write a program that creates objects of each class
and tests their member functions. Add interest to the SavingsAccount object by first invoking its
calculateInterest function, then passing the returned interest amount to the object’s credit
function.

Answer:

Test program

#include <iostream>
#include <iomanip>
#include "Account.h" // Account class definition
#include "SavingsAccount.h" // SavingsAccount class definition
#include "CheckingAccount.h" // CheckingAccount class definition
using namespace std;

int main()
{
   Account account1( 50.0 ); // create Account object
   SavingsAccount account2( 25.0, .03 ); // create SavingsAccount object
   CheckingAccount account3( 80.0, 1.0 ); // create CheckingAccount object

   cout << fixed << setprecision( 2 );

   // display initial balance of each object
   cout << "account1 balance: $" << account1.getBalance() << endl;
   cout << "account2 balance: $" << account2.getBalance() << endl;
   cout << "account3 balance: $" << account3.getBalance() << endl;

   cout << "\nAttempting to debit $25.00 from account1." << endl;
   account1.debit( 25.0 ); // try to debit $25.00 from account1
   cout << "\nAttempting to debit $30.00 from account2." << endl;
   account2.debit( 30.0 ); // try to debit $30.00 from account2
   cout << "\nAttempting to debit $40.00 from account3." << endl;
   account3.debit( 40.0 ); // try to debit $40.00 from account3

   // display balances
   cout << "\naccount1 balance: $" << account1.getBalance() << endl;
   cout << "account2 balance: $" << account2.getBalance() << endl;
   cout << "account3 balance: $" << account3.getBalance() << endl;

   cout << "\nCrediting $40.00 to account1." << endl;
   account1.credit( 40.0 ); // credit $40.00 to account1
   cout << "\nCrediting $65.00 to account2." << endl;
   account2.credit( 65.0 ); // credit $65.00 to account2
   cout << "\nCrediting $20.00 to account3." << endl;
   account3.credit( 20.0 ); // credit $20.00 to account3

   // display balances
   cout << "\naccount1 balance: $" << account1.getBalance() << endl;
   cout << "account2 balance: $" << account2.getBalance() << endl;
   cout << "account3 balance: $" << account3.getBalance() << endl;

   // add interest to SavingsAccount object account2
   double interestEarned = account2.calculateInterest();
   cout << "\nAdding $" << interestEarned << " interest to account2." 
      << endl;
   account2.credit( interestEarned );

   cout << "\nNew account2 balance: $" << account2.getBalance() << endl;
} 

Account.h

#ifndef ACCOUNT_H
#define ACCOUNT_H

class Account
{
public:
   Account( double ); // constructor initializes balance
   void credit( double ); // add an amount to the account balance
   bool debit( double ); // subtract an amount from the account balance
   void setBalance( double ); // sets the account balance
   double getBalance(); // return the account balance
private:
   double balance; // data member that stores the balance
}; 

#endif

SavingsAccount.h

#ifndef SAVINGS_H
#define SAVINGS_H

#include "Account.h" // Account class definition

class SavingsAccount : public Account
{
public:
   // constructor initializes balance and interest rate
   SavingsAccount( double, double );

   double calculateInterest(); // determine interest owed
private:
   double interestRate; // interest rate (percentage) earned by account
}; // end class SavingsAccount

#endif

CheckingAccount.h

#ifndef CHECKING_H
#define CHECKING_H

#include "Account.h" 

class CheckingAccount : public Account
{
public:
   // constructor initializes balance and transaction fee
   CheckingAccount( double, double );

   void credit( double ); 
   bool debit( double );
private:
   double transactionFee; // fee charged per transaction

   // utility function to charge fee
   void chargeFee();
}; 

#endif

Account.cpp

#include <stdexcept>
#include <iostream>
#include "Account.h"
using namespace std;

// Account constructor initializes data member balance
Account::Account( double initialBalance )
{
   // if initialBalance is greater than or equal to 0.0, set this value 
   // as the balance of the Account
   if ( initialBalance >= 0.0 )
      balance = initialBalance;
   else 
      throw invalid_argument( "Initial balance cannot be negative" );
}

// credit (add) an amount to the account balance
void Account::credit( double amount )
{
   balance = balance + amount; 
} 

// debit (subtract) an amount from the account balance
// return bool indicating whether money was debited
bool Account::debit( double amount )
{
   if ( amount > balance ) 
   {
      cout << "Debit amount exceeded account balance." << endl;
      return false;
   } // end if
   else // debit amount does not exceed balance
   {
      balance = balance - amount;
      return true;
   } // end else
} // end function debit

// set the account balance
void Account::setBalance( double newBalance )
{
   balance = newBalance;
} // end function setBalance

// return the account balance
double Account::getBalance()
{
   return balance;
} // end function getBalance

SavingsAccount.cpp

#include <stdexcept>
#include "SavingsAccount.h"
using namespace std;

// constructor initializes balance and interest rate
SavingsAccount::SavingsAccount( double initialBalance, double rate )
   : Account( initialBalance ) // initialize base class
{
   if ( rate >= 0.0 )
      interestRate = rate;
   else
      throw invalid_argument( "Interest rate must be >= 0.0" );
} 

// return the amount of interest earned
double SavingsAccount::calculateInterest()
{
   return getBalance() * interestRate;
} 

CheckingAccount.cpp

#include <iostream>
#include <stdexcept>
#include "CheckingAccount.h" 
using namespace std;

// constructor initializes balance and transaction fee
CheckingAccount::CheckingAccount( double initialBalance, double fee )
   : Account( initialBalance ) 
{
   if ( fee >= 0.0 )
      transactionFee = fee;
   else
      throw invalid_argument( "Transaction fee must be >= 0.0" );
} // end CheckingAccount constructor

// credit (add) an amount to the account balance and charge fee
void CheckingAccount::credit( double amount )
{
   Account::credit( amount ); // always succeeds
   chargeFee();
} // end function credit

// debit (subtract) an amount from the account balance and charge fee
bool CheckingAccount::debit( double amount )
{
   bool success = Account::debit( amount ); // attempt to debit

   if ( success ) // if money was debited, charge fee and return true
   {
      chargeFee();
      return true;
   } // end if
   else // otherwise, do not charge fee and return false
      return false;
} // end function debit

// subtract transaction fee
void CheckingAccount::chargeFee()
{
   Account::setBalance( getBalance() - transactionFee );
   cout << "$" << transactionFee << " transaction fee charged." << endl;
}