Access control in inheritance in C++ - Mini Project: Build & Apply

Access control in inheritance

📖 Scenario: Imagine you are designing a simple system for vehicles. You want to control how different parts of the vehicle are accessed and inherited by other classes.

🎯 Goal: You will create a base class Vehicle with members having different access levels. Then, you will create a derived class Car using public inheritance. Finally, you will print accessible members from the Car class.

📋 What You'll Learn

Create a class Vehicle with public, protected, and private members.

Create a class Car that inherits Vehicle publicly.

Access and print the public and protected members from Car.

Try to access the private member from Car and observe it is not accessible.

💡 Why This Matters

🌍 Real World

Access control in inheritance helps software designers protect sensitive data and control how different parts of a program can use or change information.

💼 Career

Understanding access control and inheritance is essential for writing secure and maintainable object-oriented code in many software development jobs.

1

Create the base class Vehicle with members

Create a class called Vehicle with a public integer member speed set to 100, a protected integer member fuel set to 50, and a private integer member engineNumber set to 12345.

C++

// Your code here

Need a hint?

Use public:, protected:, and private: sections inside the class to set access levels.

2

Create the derived class Car with public inheritance

Create a class called Car that inherits publicly from Vehicle. Inside Car, create a public method show() that will be used later to print accessible members.

C++

class Vehicle {
public:
    int speed = 100;
protected:
    int fuel = 50;
private:
    int engineNumber = 12345;
};

// Your code here

Need a hint?

Use class Car : public Vehicle to inherit publicly.

3

Implement the show() method to access members

Inside the show() method of Car, write code to print the values of speed and fuel. Also, try to access engineNumber and comment that line out because it will cause an error.

C++

class Vehicle {
public:
    int speed = 100;
protected:
    int fuel = 50;
private:
    int engineNumber = 12345;
};

class Car : public Vehicle {
public:
    void show() {
        // Your code here
    }
};

Need a hint?

You can access speed and fuel directly inside show(). The engineNumber is private and cannot be accessed here.

4

Create main function and print the results

In the main() function, create an object of Car called myCar and call its show() method to print the accessible members.

C++

#include 

class Vehicle {
public:
    int speed = 100;
protected:
    int fuel = 50;
private:
    int engineNumber = 12345;
};

class Car : public Vehicle {
public:
    void show() {
        std::cout << "Speed: " << speed << std::endl;
        std::cout << "Fuel: " << fuel << std::endl;
        // std::cout << "Engine Number: " << engineNumber << std::endl; // Not accessible
    }
};

int main() {
    // Your code here
}

Need a hint?

Remember to create the object and call show() to see the output.