Introduction
As a programmer, you may have heard of the term “inheritance” but are not sure what it means. Inheritance is a fundamental concept in object-oriented programming languages such as C++ and is used extensively throughout the language. In this blog post, we will explore the different types of inheritance used in C++ and how they can be used in your programs. From single inheritance to multiple inheritance, virtual inheritance to template inheritance, we will cover all aspects of each type so you can make informed decisions when building your code.
What is Inheritance?
Inheritance is a feature of object-oriented programming languages that allows a child class to inherit the attributes and behaviors of a parent class. In C++, inheritance is achieved by using the keyword “public” or “private” before the name of the parent class when declaring the child class.
There are two types of inheritance in C++: single inheritance and multiple inheritance. Single inheritance is when a child class inherits from only one parent class. Multiple inheritance is when a child class inherits from more than one parent class.
Inheritance can be used to create hierarchical relationships between classes, where each subclass inherits from its immediate superclass. This enables you to create a family tree of classes, with each subclass adding new features and capabilities while still retaining the attributes and behaviors of its ancestor classes.
The Different Types of Inheritance
There are different types of inheritance in C++ which are as follows:
- Single Inheritance: In single inheritance, a class is inherited from only one base class. For example, a derived class D inherits from a base class B. So, the members of class B will be accessible to class D.
- Multiple Inheritance: In multiple inheritance, a class can inherit from more than one base classes. For example, a derived class D can inherit from base classes B and C. So, the members of both classes B and C will be accessible to class D.
- Multilevel Inheritance: In multilevel inheritance, a derived class inherits from another derived class. For example, consider classes A, B and C such that class C is inherited from class B and class B is inherited from Class A. Thus, the members of all three classes will be accessible to Class C. This type of inheritance forms a chain of classes where each successive link inherits from the previous link in the chain.
- Hierarchical Inheritance: In hierarchical inheritance, two or more classes are inherited from a single base class. For example, consider a baseclass A with two derivedclasses B and C. All the members of A will be accessible to both B and C but not vice versa (i.e., members of B and C will not be accessible to each other).
- Hybrid Inheritance: Hybrid inheritance is a combination of two or more types of inheritance discussed above. For example, consider the classes A, B, C and D such that class D inherits from class C (single inheritance) and class C inherits from class A and B (multiple inheritance). So, the members of all four classes will be accessible to class D.
Single Inheritance
One of the most basic types of inheritance is single inheritance, where a derived class inherits from a single base class. In single inheritance, the derived class typically inherits all of the members of the base class, including its member functions and variables. However, it is also possible to selectively inherit only certain members from the base class.
Multiple Inheritance
Multiple inheritance is a type of inheritance in which an object or class can inherit characteristics and properties from more than one parent object or parent class. In other words, it is a situation where one subclass is derived from more than one superclass.
One real-world example of multiple inheritance is a person who has both parents that are doctors. That person would have the characteristics of both parents, including the ability to heal people.
C++ implements multiple inheritance through something called virtual inheritance. This ensures that an ambiguity doesn’t exist between two inherited variables with the same name.
Multilevel Inheritance
Multilevel inheritance is a type of inheritance in which a child class inherits from a parent class, which in turn inherits from a grandparent class. In multilevel inheritance, the grandparent class is referred to as the base class, while the parent and child classes are referred to as derived classes.
Hierarchical Inheritance
In C++, hierarchical inheritance is implemented using class derivation. Derivation is the process of creating a new class from an existing class by extending its functionality. The new class is called the derived class, and the existing class is called the base class.
The derived class inherits all the members of the base class, but it can also add new members of its own. This allows for a hierarchy of classes to be formed, with each subsequent level adding more specialized functionality.
Hybrid Inheritance
In C++, hybrid inheritance is a combination of two or more types of inheritance. This is also sometimes called virtual inheritance. Hybrid inheritance can be used to create more complex class hierarchies than single inheritance alone.
For example, suppose we have a class hierarchy for animals, with a base class Animal and subclasses Mammal and Bird. We could further subclass Mammal into Cat and Dog, and Bird into Sparrow and Falcon. If we then wanted to create a new class, Bat, which inherits from both Mammal and Bird, we would use hybrid inheritance.
There are several benefits to using hybrid inheritance. First, it allows us to reuse code from the base classes. Second, it makes our code more flexible and extensible. Third, it can help us avoid duplication of code if we need to create multiple subclasses that inherit from both Mammal and Bird.
Of course, there are also some drawbacks to using hybrid inheritance. One is that it can make our code more difficult to understand and debug. Another is that it can lead to problems with diamond-shaped class hierarchies (see the next section for more on this).
Overall, hybrid inheritance is a powerful tool that can be used to create complex class hierarchies in C++. However, it is important to use it wisely, lest we end up with code that is difficult to understand and maintain.
Advantages and Disadvantages of Inheritance
Inheritance is a feature in object-oriented programming whereby one class can inherit the attributes and behavior of another class. Inheritance is a powerful tool that can be used to extend the functionality of existing classes and to promote code reuse. However, inheritance also has some disadvantages that should be considered when deciding whether or not to use it in your own programs.
One advantage of inheritance is that it allows you to create new classes that are built upon existing ones. This can save you time and effort because you don’t have to start from scratch when creating a new class; you can simply build upon an existing one. Additionally, by inheriting from an existing class, you can automatically take on all of its functionality without having to write any additional code. This can lead to more reliable and robust code since existing classes have already been tested and proven to work properly.
A disadvantage of inheritance is that it can lead to complex class hierarchies. When using inheritance, each subclass must be aware of its parent’s internals in order to properly inherit its functionality. This can make code difficult to understand and maintain, especially as hierarchies become deep and convoluted. Additionally, any changes made to a parent class can potentially break its child subclasses, which can lead to stability issues in your program.
How to Implement Inheritance in C++?
Inheritance is a powerful tool in object-oriented programming, as it allows you to create new classes that are built upon existing ones. In C++, inheritance is implemented using the reserved keyword “virtual.”
When creating a derived class, you can specify which members of the base class will be inherited by the derived class. You can also override certain members of the base class by redeclaring them in the derived class. Finally, you can use the virtual keyword to specify which members of the base class are to be treated as virtual functions.
When overriding a member function in a derived class, you must use the same function signature as the original function in the base class. This includes the return type and the number and types of parameters. You can also declare additional overloaded versions of the overridden function in the derived class.
It is important to remember that inheritance does not automatically give your classes all of the functionality of their parent classes; it only provides a starting point from which you can add or modify functionality as needed.
Examples of Inheritance in C++
C++ supports multiple inheritance, meaning a class can inherit functionality from more than one parent class.
Consider the following example:
class A { public: void doSomething(); }; class B { public: void doSomethingElse(); }; class C : public A, public B { // … };
In this example, class C inherits both the doSomething() and doSomethingElse() methods from classes A and B. When an instance of C is created, it will have both of these methods available to it.
Conclusion
Inheritance is one of the core concepts of object-oriented programming and having a good understanding of it is essential for effective C++ programming. We have discussed the various types of inheritance in C++, including single inheritances, multiple inheritances, hierarchical inheritance and hybrid inheritance. With these tools at your disposal you will be able to create powerful and efficient code that can leverage the power of object oriented programming.