Question

4. Create a new project AccountPolymorphism and copy and paste the code from the attached AccountPolymorphism.cpp file. Compile and run. You will see that it is not showing output for Base class pointer to base class object data, not showing derived class output completely(missing word "Saving" in the output) and not showing any output for Base class pointer to derived class object(Saving). Fix these issue and submit the output.

// AccountPolymorphism.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <string>
#include <sstream>
using namespace std;

class Account
{
private:
int id;
double balance;
double annualInterestRate;

public:
Account()
{
id = 0;
balance = 0;
annualInterestRate = 0;
}

Account(int id, double balance, double annualInterestRate)
{
this->id = id;
this->balance = balance;
this->annualInterestRate = annualInterestRate;
}

  
double getMonthlyInterest() const
{
return balance * (annualInterestRate / 1200);
}

void withdraw(double amount)
{
balance -= amount;
}

void deposit(double amount)
{
balance += amount;
}

virtual string toString() const
{
stringstream ss;
ss << "Account id: " << id << " balance: " << balance;
return ss.str();
}
};

class Checkings : public Account
{
protected:
int overdraftLimit;

public:
Checkings(int id, double balance, double annualInterestRate) :Account(id, balance, annualInterestRate)
{
overdraftLimit = 5000;
}

string toString(Account Acct) const
{
stringstream ss;

cout << Acct.toString() << endl;
ss << "Account Type : " << "Checking" << endl;
return ss.str();
}
};

class Saving : public Account
{
protected:
int overdraftLimit;

public:

Saving(int id, double balance, double annualInterestRate) :Account(id, balance, annualInterestRate)
{
overdraftLimit = 5000;
}

string toString(Account Acct) const
{
stringstream ss;

cout << Acct.toString() << endl;
ss << "Account Type : " << "Saving" << endl;
return ss.str();
}
};

int main()
{
// Saving saving;
// Checkings checking;

cout << "Testing Account Class object " << endl << endl;
Account TestAccount{ 121,2000.00,0.5 };
cout << TestAccount.toString() << endl;
cout << "Depositing $1000 to Account object" << endl << endl;
TestAccount.deposit(1000.00);
cout << "Amount after depositing $1000 to Account object " << endl << endl;
cout << TestAccount.toString() << endl;
cout << "Withdrawing $2000 from the Account object " << endl << endl;
TestAccount.withdraw(2000.00);
cout << "Amount after witdrawing $2000 from the Account object " << endl << endl;
cout << TestAccount.toString() << endl << endl;

cout << "Creating Savings object " << endl << endl;
Saving saving{ 122, 44000, 0.5 };
cout << saving.toString(saving) << endl;

cout << "Creating Checking object " << endl << endl;
Checkings checking{ 444, 88000, 0.8 };
cout << checking.toString(checking) << endl << endl;

// Using Base Class pointer at Base Class object

const Account* AccountPtr{ &TestAccount };
cout << "Base Class pointer at Base Class object" << endl << endl;
AccountPtr->toString();
cout << endl << endl;

// Using Derived Class pointer at Derived Class object

const Saving* SavingPtr{ &saving };
cout << "Derived Class pointer at Derived Class object" << endl << endl;
SavingPtr->toString(saving);
cout << endl << endl;

// Using Base Class pointer at Derived Class object

cout << "Base Class pointer at Derived Class object" << endl << endl;
AccountPtr = &saving;
AccountPtr->toString();
cout << endl << endl;

cout << "" << endl;

system("pause");

return 0;
}

Answer 1

Program needs to be corrected :

#include <iostream>
#include <string>
#include <sstream>
using namespace std;

class Account
{
private:
int id;
double balance;
double annualInterestRate;

public:
Account()
{
id = 0;
balance = 0;
annualInterestRate = 0;
}

Account(int id, double balance, double annualInterestRate)
{
this->id = id;
this->balance = balance;
this->annualInterestRate = annualInterestRate;
}

  
double getMonthlyInterest() const
{
return balance * (annualInterestRate / 1200);
}

void withdraw(double amount)
{
balance -= amount;
}

void deposit(double amount)
{
balance += amount;
}

string toString() const // no need of virtual keyword since no functions with same prototype exist in child class
{
stringstream ss;
ss << "Account id: " << id << " balance: " << balance;
return ss.str();
}
};

class Checkings : public Account
{
protected:
int overdraftLimit;

public:
Checkings(int id, double balance, double annualInterestRate) :Account(id, balance, annualInterestRate)
{
overdraftLimit = 5000;
}

string toString(Account Acct) const
{
stringstream ss;

cout << Acct.toString() << endl;
ss << "Account Type : " << "Checking" << endl;
return ss.str();
}
};

class Saving : public Account
{
protected:
int overdraftLimit;

public:

Saving(int id, double balance, double annualInterestRate) :Account(id, balance, annualInterestRate)
{
overdraftLimit = 5000;
}

string toString(Account Acct) const
{
stringstream ss;

cout << Acct.toString() << endl;
ss << "Account Type : " << "Saving" << endl;
return ss.str();
}
};

int main()
{
// Saving saving;
// Checkings checking;

cout << "Testing Account Class object " << endl << endl;
Account TestAccount{ 121,2000.00,0.5 };
cout << TestAccount.toString() << endl;
cout << "Depositing $1000 to Account object" << endl << endl;
TestAccount.deposit(1000.00);
cout << "Amount after depositing $1000 to Account object " << endl << endl;
cout << TestAccount.toString() << endl;
cout << "Withdrawing $2000 from the Account object " << endl << endl;
TestAccount.withdraw(2000.00);
cout << "Amount after witdrawing $2000 from the Account object " << endl << endl;
cout << TestAccount.toString() << endl << endl;

cout << "Creating Savings object " << endl << endl;
Saving saving{ 122, 44000, 0.5 };
cout << saving.toString(saving) << endl;

cout << "Creating Checking object " << endl << endl;
Checkings checking{ 444, 88000, 0.8 };
cout << checking.toString(checking) << endl << endl;

// Using Base Class pointer at Base Class object

const Account *AccountPtr =&TestAccount ;
cout << "Base Class pointer at Base Class object" << endl << endl;
cout<<AccountPtr->toString(); //cout is used because here toString() is returning a string object with a copy of the current contents of the stream
cout << endl << endl;

// Using Derived Class pointer at Derived Class object

const Saving* SavingPtr{ &saving };
cout << "Derived Class pointer at Derived Class object" << endl << endl;
SavingPtr->toString(saving);
cout << endl << endl;

// Using Base Class pointer at Derived Class object

cout << "Base Class pointer at Derived Class object" << endl << endl;
AccountPtr = &saving;
cout<<AccountPtr->toString();   //cout is used because here toString() is returning a string object with a copy of the current contents of the stream
cout << endl << endl;

cout << "" << endl;

system("pause");

return 0;
}

Output :

Testing Account Class object

Account id: 121 balance: 2000
Depositing $1000 to Account object

Amount after depositing $1000 to Account object

Account id: 121 balance: 3000
Withdrawing $2000 from the Account object

Amount after witdrawing $2000 from the Account object

Account id: 121 balance: 1000

Creating Savings object

Account id: 122 balance: 44000
Account Type : Saving

Creating Checking object

Account id: 444 balance: 88000
Account Type : Checking

Base Class pointer at Base Class object

Account id: 121 balance: 1000

Derived Class pointer at Derived Class object

Account id: 122 balance: 44000

Base Class pointer at Derived Class object

Account id: 122 balance: 44000

Explanation :

• The virtual keyword is not necessary here because the prototype used for function toString() in Account and its child classes namely Checking and Saving class are different.
• Checking and Saving Class have toString(Account Acct) const definition while Account class has toString() const definition. Both are different functions not because the child contains one parameter for function toString() while the parent does not have any parameter for function toString().
• So while defining toString() in Account Class, I have removed the virtual keyword.
• LIne having statement   " AccountPtr->toString(); " is being replaced by " cout<<AccountPtr->toString(); ". The reason is that toString() of Account Class is returning a string object with a copy of the current contents of the stream which need to be printed.
• Now Base Class pointer pointing to any object either of is own type or its chid type can use the toString() method to obtain a string object and print it.