OOP

Function overriding

Function overriding is a powerful mechanism in object-oriented C++ that allows derived classes to redefine inherited functions from base classes.

Understanding Function Overriding

• Core Concept: In inheritance, when a derived class inherits a function from its base class, it has the capability to provide its own implementation for that function. This redefinition is called function overriding.
• Key Points:
  • The function in the derived class has the same name and signature (return type and parameter list) as the function in the base class.
  • The overriding function provides specialized behavior specific to the derived class.
• Benefits:
  • Enables polymorphism, a core principle of object-oriented programming that allows for flexible and dynamic function calls.
  • Promotes code reusability by inheriting common functionality from the base class while customizing behavior in derived classes.

Example: Overriding deposit Function in Banking Accounts

Let’s illustrate function overriding with a banking account scenario:

class BankAccount {
public:
  virtual void deposit(double amount) {
    // Base class implementation (common logic for all accounts)
    balance += amount;
  }

protected:
  double balance = 0.0;
};

class SavingAccount : public BankAccount {
public:
  void deposit(double amount) override {
    // Derived class implementation (specific to savings accounts)
    balance += amount + (amount * interestRate);
  }

private:
  double interestRate = 0.01; // Example interest rate
};

int main() {
  SavingAccount mySavings;
  mySavings.deposit(100.0); // Calls SavingAccount's deposit with interest

  BankAccount genericAccount; // Base class object
  genericAccount.deposit(100.0); // Calls BankAccount's deposit (no interest)
}

Explanation:

1. The BankAccount class serves as the base class with a deposit function that performs the common task of adding the amount to the balance. It’s declared as virtual to allow overriding in derived classes.
2. The SavingAccount class inherits from BankAccount. It overrides the deposit function, providing its own implementation that adds the interest rate to the deposited amount.

Key Points to Remember:

• The function call in the main function depends on the object’s type at runtime (runtime polymorphism). When you call deposit on a SavingAccount object, the overridden version with interest calculation is executed.
• Overriding enables you to create a hierarchy of classes with specialized functionalities while maintaining a common foundation in the base class.

Assignment Due 19 November 2024

Assignment Title: “E-Commerce Discount System”

Objective:
Develop a C++ program simulating an e-commerce discount system where various types of users receive different discount rates on their purchases. The assignment will help practice inheritance, function overriding, and virtual functions.

Requirements:

1. Base Class: User
   • Data members: name (string), userID (int)
   • Virtual function: getDiscount(), which returns a default discount rate (e.g., 0%).
2. Derived Classes:
   • GuestUser (inherits User)
     • Overrides getDiscount() to apply a low discount rate (e.g., 5%).
   • RegisteredUser (inherits User)
     • Additional data member: purchaseAmount (double)
     • Overrides getDiscount() to apply a higher discount based on purchaseAmount (e.g., 10% if purchaseAmount > 100).
   • PremiumUser (inherits RegisteredUser)
     • Overrides getDiscount() to provide the highest discount rate (e.g., 20%).
3. Program Execution:
   • Instantiate objects of each user type (e.g., GuestUser, RegisteredUser, and PremiumUser).
   • Use pointers to the base class User to call the getDiscount() function and display the appropriate discount for each type.