C++ Multiple, Multilevel and Hierarchical Inheritance

C++ Multiple, Multilevel and Hierarchical Inheritance

In this article, you will find out about various models of inheritance in C++ programming: Multiple, Multilevel, and Hierarchical inheritance with examples.

Inheritance is one of the center elements of an object-oriented programming language. It allows software developers to get another class from the current class. The inferred class acquires the highlights of the base class (existing class).

There are different models of inheritance in C++ programming.

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C++ Multilevel Inheritance

In C++ programming, not just you can get a class from the base class however you can likewise get a class from the determined class. This type of inheritance is known as multilevel inheritance.

class A
{ 
... .. ... 
};
class B: public A
{
... .. ...
};
class C: public B
{
... ... ...
};

Here, class B is derived from the base class A and the class C is derived from the derived class B.

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Example 1: C++ Multilevel Inheritance

#include <iostream>
using namespace std;

class A
{
    public:
      void display()
      {
          cout<<"Base class content.";
      }
};

class B : public A
{

};

class C : public B
{
 
};

int main()
{
    C obj;
    obj.display();
    return 0;
}

Output

Base class content.

In this program, class C is derived from class B (which is derived from base class A).

The obj object of class C is defined in the main() function.

When the display() function is called, display() in class A is executed. It’s because there is no display() function in class C and class B.

The compiler first looks for the display() function in class C. Since the function doesn’t exist there, it looks for the function in class B (as C is derived from B).

The function also doesn’t exist in class B, so the compiler looks for it in class A (as B is derived from A).

If the display() function exists in C, the compiler overrides display() of class A (because of member function overriding).

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C++ Multiple Inheritance

In C++ programming, a class can be gotten from more than one guardians. For instance: A class Bat is derived from base classes Mammal and WingedAnimal. It makes sense because the bat is a mammal as well as a winged animal.

Example 2: Multiple Inheritance in C++ Programming

#include <iostream>
using namespace std;

class Mammal {
  public:
    Mammal()
    {
      cout << "Mammals can give direct birth." << endl;
    }
};

class WingedAnimal {
  public:
    WingedAnimal()
    {
      cout << "Winged animal can flap." << endl;
    }
};

class Bat: public Mammal, public WingedAnimal {

};

int main()
{
    Bat b1;
    return 0;
}

Output

Mammals can give direct birth.
Winged animal can flap.

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Ambiguity in Multiple Inheritance

The most evident issue with multiple inheritances happens during function overriding.

Assume, two base classes have an equivalent capacity which isn’t overridden in derived class.

If you attempt to call the capacity using the object of the determined class, compiler shows error. This is on the grounds that compiler doesn’t realize which capacity to call. For instance,

class base1
{
  public:
     void someFunction( )
     { .... ... .... }  
};
class base2
{
    void someFunction( )
     { .... ... .... } 
};
class derived : public base1, public base2
{
    
};

int main()
{
    derived obj;

    obj.someFunction() // Error!  
}

This problem can be solved using scope resolution function to specify which function to class either base1or base2

int main()
{
    obj.base1::someFunction( );  // Function of base1 class is called
    obj.base2::someFunction();   // Function of base2 class is called.
}

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C++ Hierarchical Inheritance

If more than one class is acquired from the base class, it’s known as hierarchical inheritance. In hierarchical inheritance, all highlights that are common in child classes are included in the base class.

For instance: Physics, Chemistry, Biology are derived from Science class.

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Syntax of Hierarchical Inheritance

class base_class {
     ... .. ...
}

class first_derived_class: public base_class {
     ... .. ...
}

class second_derived_class: public base_class {
     ... .. ...
}

class third_derived_class: public base_class {
     ... .. ...
}

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C++ Inheritance