Multilevel Inheritance in C++

Syntax for Multilevel Inheritance:

class A // base class
{
     ...........
};
class B: acess_specifier A // derived class from class A
{
     ...........
 } ;
 class C: access_specifier B // derived from derived class B
 {
     ...........
 } ;

Example of Multilevel Inheritance in C++

• C++

C++

#include <iostream>
using namespace std;
class base 
{
  public:
  int x;
  void getdata()
  {
     cout << "Enter value of x= "; cin >> x;
  }
};
class derive1: public base 
{
  public:
  int y;
  void readdata()
  {
  cout << "Enter value of y= "; cin >> y;
  }
};
class derived2: public derive1   
{
  private:
  int z;
  public:
  void indata()
  {
     cout << "Enter value of z= "; cin >> z;
  }
  void product()
  {
  cout << "Product= " << x * y * z;
  }
};
int main()
{
     derived2 a;      
     a.getdata();
     a.readdata();
     a.indata();
     a.product();
     return 0;
} 

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Output

Enter value of x= 2
Enter value of y= 3
Enter value of z= 3
Product= 18

The above was an example of multilevel inheritance. ​​​​Here derived2 class is derived from the derived1 class, which is derived from the base class.

Know about Single Inheritance in Java in detail.

How Does Multilevel Inheritance Work in C++?

In C++, multilevel inheritance involves a chain of classes where each class inherits from the previous one. This means that a derived class inherits properties and behaviors from its immediate base class and all its ancestor classes.

Here’s a simple example to illustrate multilevel inheritance:
 

• C++

C++

#include <iostream>
using namespace std;

class A {
public:
    void displayA() {
        cout << "Class A" << endl;
    }
};

class B : public A {
public:
    void displayB() {
        cout << "Class B" << endl;
    }
};

class C : public B {
public:
    void displayC() {
        cout << "Class C" << endl;
    }
};

int main() {
    C obj;
    obj.displayA(); // Inherited from class A
    obj.displayB(); // Inherited from class B
    obj.displayC(); // Defined in class C
    return 0;
}

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In this example, class C inherits from class B, which in turn inherits from class A. Thus, an object of class C can access members of both class A and class B.

Example of Constructor in Multilevel Inheritance

In multilevel inheritance, a class derives from a base class, which itself is derived from another class. Constructors in multilevel inheritance are invoked in a specific order: the constructor of the base class is called first, followed by the derived class constructors.

Example

• C++

C++

#include <iostream>
using namespace std;

// Base class
class Animal {
public:
    Animal() {
        cout << "Animal constructor called." << endl;
    }
};

// Derived class
class Mammal : public Animal {
public:
    Mammal() {
        cout << "Mammal constructor called." << endl;
    }
};

// Further derived class
class Dog : public Mammal {
public:
    Dog() {
        cout << "Dog constructor called." << endl;
    }
};

int main() {
    Dog d;  // Object of the Dog class
    return 0;
}

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Output:

Animal constructor called.
Mammal constructor called.
Dog constructor called.

Difference Between Multilevel and Multiple Inheritance in C++

Frequently Asked Questions 

If there are three classes. Class Z is derived from class Y, and Y is derived from X, Which class destructor will be called at last if the object of Z is destroyed.

The destructors are called within the reverse order of the constructors being called. Therefore in multilevel inheritance, the constructors are created from parent to child, which leads to destruction from child to parent. Therefore, class X destructor will be known as at last.

What are the advantages of multilevel inheritance in C++? 

The advantage of multilevel inheritance in C++ is code reusability. It lets you inherit from multiple parent classes, reducing redundant code.

What is multilevel inheritance in C++ real-world example?

The multilevel inheritance in C++ real-world example is to imagine a Vehicle class (car, bike) inheriting from Engine, then a SportsCar inheriting from both.

What is multilevel and hybrid inheritance in C++?

Multilevel is a chained inheritance (A -> B -> C). Hybrid inheritance means inheriting from multiple parents at once (like combining animal traits). 

Conclusion

We learned what multilevel inheritance is and how to implement it in C++.

The main benefit of multilevel inheritance is that it allows the flow of resources to the depths of the hierarchy of classes. Use Code360 to practice various DSA questions asked in many interviews. You will also get interview experiences from people working in big companies.

Recommended Readings:

• CPP Abstract Class
• Dynamic Binding in C++
• Introduction to C++
• Introduction to C#