Multiple Inheritance in C++ with Real-life Analogy

Multiple Inheritance in C++ with Real-life Analogy

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Updated on Jul 11, 2023 16:53 IST

In this article we will learn Multiple inheritance with real life analogy.This article also explains this concept with programming example with proper explanation of code.

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Multiple inheritance is a powerful OOPS feature of C++ that allows programmers to implement rich behavior in their programs without writing many lines of code. It enables a class to inherit the features of multiple parent classes.

Multiple inheritance is a feature in which a class inherits the feature points of several parent classes. It provides more flexibility to programmers than single inheritance because multiple parents can be inherited in one step. For example, a class with multiple superclasses is called a base class. A subclass that inherits the features of several superclasses is called a base class. In C++, multiple inheritance is supported by templates, where parameters can be overloaded via multiple values. Furthermore, programmers can implement multiple inheritance using templates and non-template mechanisms such as virtual functions and multiple constructors. In this article, I will discuss what multiple inheritance is and how it works in C++.

Table of contents

What is Multiple Inheritance?

In object-oriented programming, inheritance is the mechanism by which one class can inherit the properties and behavior of another class. In single inheritance, a class can inherit from only one base class. In multiple inheritance, a class can inherit from multiple base classes. This allows for greater flexibility and code reuse but also increases the complexity of the code.

Syntax of Multiple Inheritance in C++

 
class A
{
... .. ...
};
class B
{
... .. ...
};
class C: public A,public B
{
... ... ...
};
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Real life analogy of Multiple Inheritance

In the above diagram, we can see that we have one base class named music player. A class can have multiple derived classes. In this, we have different derived classes such as home theater and MP3 Players. These classes inherit properties from the music player class. That means they have access to the properties and behavior of that base class, enabling versatile and dynamic music player systems. Then we have one more derived class which is the Bluetooth speaker. This class inherits the properties of a home theater class and MP3 player class.You must be confused with the word properties.

So let’s understand this with an example.

The music player has the option of forwarding/reversing the music. In the same way, home theater and MP3 player will also have the same properties,as these two classes are inherited from base class music player. Then home theater has a property of good bass. And MP3 has an option for FM radio. In the same way, Bluetooth speakers(which is inherited from Home theater and MP3 class) also have the option of FM radio and high bass. Plus, it will have its own properties.

When to use Multiple Inheritance?

  • Multiple inheritance is useful when a subclass combines multiple contracts and needs to inherit some or all of those contracts’ implementations. For example, the AmericanStudent class must inherit from both the Student class and the American class.
  • When you want to save time by not writing the same code for different classes.

Advantages of Multiple Inheritance

1.Code Reusability: Multiple inheritance allows classes to inherit properties and behavior from multiple base classes, making them more versatile and powerful. This makes writing complex and meaningful code easier and improves code reusability.

2. Dynamic Polymorphism: Multiple inheritance allows the implementation of dynamic polymorphism. A class can have multiple base classes, each with its own virtual functions that derived classes can override, and derived classes can have multiple polymorphic forms.

3. Model complex relationships: Multiple inheritance makes it easier to model complex relationships between classes. For example, a class representing a car can inherit multiple base classes .That base classes could be vehicle class and Atomobile class.

4. Flexibility: Multiple inheritance provides more flexibility in how classes are implemented, allowing classes to inherit properties and methods from multiple classes. This is useful when a class has multiple functions.

5. Mixed Properties and Behaviors: Multiple inheritance allows you to mix properties and behaviors from different classes. This is useful when a class needs to inherit the properties of one class and the behavior of another class.

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Disadvantages of Multiple Inheritance

  1. Ambiguity: A class may have multiple versions of the same property or behavior if inherited from multiple base classes. This can lead to ambiguity and confusion, making the code more difficult to understand and maintain.
  2. Order of Inheritance: When a class inherits from multiple base classes, it is important to know the order in which inheritance occurs. This can significantly affect the behavior of your class and lead to unexpected and difficult-to-debug errors.
  3. Increased complexity: Multiple inheritance complicates code and makes it more difficult to understand and maintain. The Diamond Problem: The Diamond Problem is a problem that arises in multiple inheritance when two classes inherit from one superclass and subclasses derive from both. An ambiguity arises in the case of virtual inheritance.
  4. Increased memory requirements: Because derived classes contain all base class data members, multiple inheritance can increase memory requirements.
  5. Difficult to understand and debug: Multiple inheritance creates complex relationships between classes, making code more difficult to understand and debug.

Multiple Inheritance Program in C++

Program to calculate the area of Square

 
class Shape {
public:
double getArea() { return 0; }
};
class Color {
public:
std::string getColor() { return "none"; }
};
class Square : public Shape, public Color {
private:
double side;
public:
Square(double s) : side(s) {}
double getArea() { return side * side; }
std::string getColor() { return "red"; }
};
int main() {
Square sq(5);
std::cout << "Area: " << sq.getArea() << std::endl;
std::cout << "Color: " << sq.getColor() << std::endl;
return 0;
}
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Explanation

In this example, the class Square inherits from both the Shape and Color classes. It has its own implementation of the methods getArea() and getColor(), which override the versions inherited from the base classes. When we create an object of class Square and call these methods, the methods defined in Square are used.

In the example, Square (double s) : side(s) {} is the constructor of the Square class. side(s) is used to initialize the side member variable of the class with the value passed in as the parameter s.

In the constructor, : symbol is used to separate the constructor’s signature (i.e. Square (doubles)) from the initializer list. The initializer list must come after the constructor’s signature and before the body of the constructor.

Conclusion

Multiple inheritance is a powerful and unique feature of C++ that allows for greater code reuse and flexibility. However, it also comes with certain challenges and pitfalls that must be understood to use effectively. By using best practices and understanding the potential issues, it is possible to create elegant and expressive code that takes advantage of the benefits of multiple inheritance.

FAQs

What are the benefits of multiple inheritance in C++?

Reusability: With multiple inheritance, you can reuse existing classes and combine their features to create a new class. This can lead to more modular and maintainable code by leveraging the functionality of different base classes. Flexibility: Multiple inheritance allows you to model complex relationships between classes that cannot be represented by single inheritance alone. It provides a way to incorporate multiple aspects or characteristics into a derived class. Specialization: By inheriting from multiple base classes, a derived class can specialize in different areas, gaining capabilities from each base class. This can be particularly useful in scenarios where different base classes represent different aspects of functionality. Polymorphism: Multiple inheritance can enable polymorphic behavior by inheriting from multiple interfaces or abstract classes. This allows objects of the derived class to be used interchangeably with objects of any of its base classes.

Can multiple inheritance be used with interfaces or abstract classes in C++?

Yes, multiple inheritance can be used with interfaces or abstract classes in C++. By inheriting from multiple interfaces or abstract classes, a derived class can adhere to multiple contracts or implement multiple sets of abstract methods. This allows for greater flexibility and code reuse in designing class hierarchies.

How can the "using" keyword be used in the context of multiple inheritance?

The "using" keyword can be used to bring base class members into the scope of the derived class. It allows the derived class to reuse and override base class methods or attributes. By using the "using" keyword, you can specify which base class member you want to use and avoid ambiguity when there are name clashes between base classes.

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