INHERITANCE IN PROGRAMMING: CHARACTERISTICS, TYPES, EXAMPLES - TECHNOLOGY - 2025

The inheritance in object - oriented programming is a way to organize objects in a hierarchy from the general to the specific. It is the gadget used to extend a class into another class, preserving an analogous execution.

In most class-based object-oriented languages, an object created through inheritance, called a child object, gets all the properties and behaviors of the parent object.

Simple proof of inheritance in object orientation. Source: Pluke / CC0 Creative Commons CC0 1.0 Universal Public Domain

Therefore, it is a quality that represents the relationship between different classes. Inheritance allows a class to have the same behavior as another class and to extend or adapt that behavior to provide a special action for specific needs.

Inheritance can help represent objects that have some differences and some similarities in the way they work. You can put all the functionality that the objects have in common in a base class, and then define one or more subclasses with your own custom functionality.

Characteristics of inheritance

Inheritance is one of the key characteristics of object-oriented programming, used to define a new class from existing classes.

That is, new classes can be derived from existing base classes, adding new features. You don't have to write from scratch. Therefore, inheritance provides a way to easily reuse existing code.

If you already have a class that does almost everything you want, you can create a subclass in which some of its behavior is partially overridden, or perhaps some new functionality is added.

A derived class inherits all the methods of the base class, except for the following:

- Constructors, destructors and copy constructors of the base class.

- Operators overloaded from the base class.

- Base class friendly functions.

Hierarchy

As a family tree does, inheritance serves to form a hierarchy of classes. It is important to note that the attributes determined for a base class will be present automatically in the derived class. Also, the methods for the base class will work for the derivatives.

A class is said to be a subclass of the class it inherits from. On the other hand, this class will be your superclass. The most generic class can be referred to as the base class, since it is at the base of the hierarchy.

Polymorphism

Inheritance is very popular in some languages ​​with static types, because it allows the programmer to avoid some of the restrictions of the static type.

An object that inherits from another object is considered a subtype of that object. An example could be the objects "instructor" and "student", each of which inherits from "person".

If instructor and student are of the same person type, you can write a function that accepts the person type as a parameter and that works on the instructor and student objects, because they are both person heirs.

Types of inheritance

Unique inheritance

When a derived class inherits the properties and behavior of a single base class. That is, one class extends to only one other class.

Multi-level inheritance

Refers to the gadget where you can inherit from a derived class, making this derived class the base class for a new class. That is, it results when a derived class is created from another derived class.

Hierarchical inheritance

In this inheritance, many subclasses inherit from a single class. That is, it happens when a single base class is inherited by more than one derived class.

Hybrid inheritance

It is the resulting inheritance when any of the three previous inheritances are combined (single, hierarchical and multilevel).

Multiple inheritance

It corresponds to the inheritance figure when a class inherits from more than one superclass. The drawback with this type of inheritance is that the derived class will have to handle the dependency it has on two base classes.

On the other hand, this type of inheritance allows programmers to build classes that combine the aspects of multiple classes and their corresponding hierarchies.

Types of inheritance from a base class

Public inheritance

When a class is derived from a public base class, the public members of the base class become public members of the derived class and the protected members of the base class become protected members of the derived class.

The private members of a superclass will never be accessible directly from a derived class, but can be accessed by calls made to the public and protected members of the base class.

Protected inheritance

When you create a class that inherits from a protected superclass, both the public and protected members of this superclass will become protected members of the derived class.

Private inheritance

When a subclass is created from a private superclass, the public and protected members of this superclass will become private members of the subclass.

Examples

Python example

To show how the inheritance principle works, we will take robots or a better class of robots in the Python programming language. To do this, a class called RobotMédico (PhysicianRobot) will be specified, which is derived from the Robot superclass.

If you look at the code of the RobotMédico class, you can see that no attribute or method has been defined in this class.

Since the RobotMedico class is a subclass of Robot, it inherits both the __init__ and say_hi methods in this case. Inheriting these methods means that they can be used as if they had been defined in the RobotMédico class.

When an instance of RobotMedico is created, the __init__ function will also create a name attribute. The say_hi method can be applied to the object “y” of RobotMédico, as can be seen in the result of the previous code.

Example in C ++

A class can inherit from more than one class, which means that it can inherit data and functions from multiple superclasses. To define a derived class, you use a class derivation list to specify the base classes.

A class derivation list in C ++ names one or more base classes and has the following form: class derived-class: access-specifier base-class, where access-specifier is public, protected, or private, and base-class is the name of a previously defined class. If access-specifier is not used, private is taken by default.

The superclass "Shape" and its derived class "Rectangle" can be considered as follows:

When the above code is compiled and executed, the following output occurs: "Total area: 35".

References

1. Dave Braunschweig (2020). Inheritance and Polymorphism. Rebus Community. Taken from: press.rebus.community.
2. Python Course (2020). Inheritance. Taken from: python-course.eu.
3. Data Mentor (2020). R Inheritance. Taken from: datamentor.io.
4. Tutorials Point (2020). C ++ Inheritance. Taken from: tutorialspoint.com.
5. Net-informations (2020). Different Types of Inheritance. Taken from: net-informations.com.