Encapsulation and Privacy in C++

Lesson Overview

Hello! In this lesson, we're revisiting Encapsulation, Private Attributes, and Private Methods in Object-Oriented Programming (OOP). Imagine encapsulation as an invisible fence safeguarding a garden from outside interference, keeping data and methods safe within. Within this garden, certain plants (Private Attributes and Private Methods) are only for the gardener's eyes. These are crucial for making your classes more robust and secure!

Into the Encapsulation

Encapsulation in OOP wraps up data and methods into a class . This organizational approach tidies the code and reinforces security. If you were to code a multiplayer game, for example, you could create a Player class, encapsulating data (health, armor, stamina) and methods (receiveDamage, shieldHit, restoreHealth). C++ #include <iostream> using namespace std; class Player {public: // Constructor Player(int health, int armor, int stamina) : health(health), armor(armor), stamina(stamina) {} // Public methods void receiveDamage(int damage) {health -= damage; // Reduce health} void shieldHit(int armorDecrease) {armor -= armorDecrease; // Decrease armor} void restoreHealth(int healthIncrease) {health += healthIncrease; // Restore health} private: // Private attributes int health; int armor; int stamina;}; int main() {Player player(100, 50, 77); player.receiveDamage(10); player.shieldHit(5); player.restoreHealth(15); return 0;} #include <iostream> using namespace std; class Player {public: // Constructor Player(int health, int armor, int stamina) : health(health), armor(armor), stamina(stamina) {} // Public methods void receiveDamage(int damage) {health -= damage; // Reduce health} void shieldHit(int armorDecrease) {armor -= armorDecrease; // Decrease armor} void restoreHealth(int healthIncrease) {health += healthIncrease; // Restore health} private: // Private attributes int health; int armor; int stamina;}; int main() {Player player(100, 50, 77); player.receiveDamage(10); player.shieldHit(5); player.restoreHealth(15); return 0;} Now, player is an instance of the Player class on which you can call methods.

Remark the Privacy

Private Attributes

Private Attributes, which can only be altered via class methods, limit outside interference. For instance, a BankAccount class might feature a balance private attribute that one could change only through deposits or withdrawals. C++ #include <iostream> using namespace std; class BankAccount {public: // Constructor BankAccount(int accountNumber, double balance) : accountNumber(accountNumber), balance(balance) {} // Public method to deposit money void deposit(double amount) {balance += amount; // Deposit money} // Method to print balance (for demonstration purposes) void printBalance() const {cout << "Balance: " << balance << endl;} private: // Private attributes int accountNumber; double balance;}; int main() {BankAccount bankAccount(1234, 100.0); bankAccount.printBalance(); // Uncommenting the following line would cause an error because balance is private // cout << bankAccount.balance << endl; return 0;} #include <iostream> using namespace std; class BankAccount {public: // Constructor BankAccount(int accountNumber, double balance) : accountNumber(accountNumber), balance(balance) {} // Public method to deposit money void deposit(double amount) {balance += amount; // Deposit money} // Method to print balance (for demonstration purposes) void printBalance() const {cout << "Balance: " << balance << endl;} private: // Private attributes int accountNumber; double balance;}; int main() {BankAccount bankAccount(1234, 100.0); bankAccount.printBalance(); // Uncommenting the following line would cause an error because balance is private // cout << bankAccount.balance << endl; return 0;} Here, balance is private, thus ensuring the integrity of the account balance.

Private Methods

Like private attributes, private methods are accessible only within their class. Here's an example: C++ #include <iostream> using namespace std; class BankAccount {public: // Constructor BankAccount(int accountNumber, double balance) : accountNumber(accountNumber), balance(balance) {} // Public method calling the private method void addYearlyInterest() {addInterest(0.02); // Adds 2% interest} // Method to print balance (for demonstration purposes) void printBalance() const {cout << "Balance: " << balance << endl;} private: // Private method void addInterest(double interestRate) {balance += balance * interestRate; // Calculation of interest} // Private attributes int accountNumber; double balance;}; int main() {BankAccount bankAccount(1234, 100.0); bankAccount.addYearlyInterest(); bankAccount.printBalance(); // Uncommenting the following line would cause an error because addInterest is private // bankAccount.addInterest(0.1); return 0;} #include <iostream> using namespace std; class BankAccount {public: // Constructor BankAccount(int accountNumber, double balance) : accountNumber(accountNumber), balance(balance) {} // Public method calling the private method void addYearlyInterest() {addInterest(0.02); // Adds 2% interest} // Method to print balance (for demonstration purposes) void printBalance() const {cout << "Balance: " << balance << endl;} private: // Private method void addInterest(double interestRate) {balance += balance * interestRate; // Calculation of interest} // Private attributes int accountNumber; double balance;}; int main() {BankAccount bankAccount(1234, 100.0); bankAccount.addYearlyInterest(); bankAccount.printBalance(); // Uncommenting the following line would cause an error because addInterest is private // bankAccount.addInterest(0.1); return 0;} Here, addYearlyInterest is a public method that calls the private method addInterest .

Lesson Summary and Practice

Great job refreshing your understanding of encapsulation, private attributes, and private methods concepts in C++! Correctly understanding and applying these foundational principles of OOP make your code concise, robust, and secure. Coming up next is hands-on practice. Keep up the good work - exciting exercises are just around the corner!