In this article, we aim at introducing these two advanced concepts in C++, their relevance, as well as their contribution to the design and construction of object-oriented systems.
What is Inheritance?
As the name suggests, inheritance allows one entity to take up properties and characteristics of another entity. In C++, this is accomplished when one class, which in this case C++ calls a ‘derived class,’ inherits the attributes and behaviors that belong to another entity known as a ‘base class.’ This mechanism resembles a child inheriting features and traits from its parent. The derived class inherits the methods and attributes from the base class but also has the option to insert new methods or combine the previous ones with the inherited ones.Polymorphism is often referred to as code overriding. This is a huge advantage in programming languages such as C++ because it allows a child class to alter the function of the parent class when inheriting from it. Code reuse is the primary benefit of inheritance, as developers do not need to recreate such code because the derived class already possesses the functionality of the base class. This improves the structure of the code, its maintenance, and reduces redundancy.
Inheriting class types in C++ is of a somewhat more diverse nature than in most scripting languages. The following are some forms of inheritance in C++:
- Single inheritance: where a class is only permitted to inherit from a single class.
- Multiple inheritance: which permits the class to inherit more than one class type.
- Multilevel inheritance: where a child class can also serve as a parent class for another child class and thus inherits the grandparent class.
- Hierarchical inheritance: where a child class or classes are created with a superclass as the parent.
With inheritance, the developer takes on a hierarchy of classes that can model relationships from the real world. For example, in a hierarchy of classes as animals, the category of Dog could inherit the class type of Animal . The Animal class may have common properties like age and color and methods like eat and sleep.
What does Polymorphism mean in programming?
Polymorphism occurs in the noun, "multiple forms" in OOP. In simple terms, it refers to the ability of objects of different classes to provide different implementations of a method or behavior but using the same interface. Put differently, polymorphism enables us to treat an object of a particular type as an object of a different type while still acting as though it was an object of a common base type.Polymorphism can be broadly classified into two types:
1. Static polymorphism: also known as
Compile-time polymorphism . 2. Run-time polymorphism: achieved through dynamic polymorphism.
Static polymorphism refers to overloading methods or overriding the operator. In this case, the determination of which version of the method needs to be called (based on the number and type of arguments) is done during compile time.
Run-time polymorphism involves method invocation and inheritance. With run-time polymorphism, a specific function will be invoked on the derived class at runtime, even though the function has already been defined in a base class.
Polymorphism is a very important functionality in programming. It allows developers to write code that is broader and reusable, where functions and methods can be applied to objects of different types without needing to specify the type in advance.
The Relationship Between Inheritance and Polymorphism
The concepts of inheritance and polymorphism are interrelated, and their combination helps in modern system design since it makes such systems both flexible and extensible.
Every class inherits from an elementary class, and every such elementary class can define methods. For example, the qualities of the derived class are inherited from the base class. However, in the derived class, it can override some of the base behaviors while still maintaining the derived class-based interface. This adjustment is what enables polymorphism. This feature allows treating objects of the base class and objects of derived classes as different types while still allowing appropriate method calls based on the type of the object during program execution.
Put differently, polymorphism allows a derived class to "alter/modify" the functionality of the base class, meaning that the system can support different types of objects through the same interface. This makes it possible to create new types of objects without modifying the existing ones, following the open/closed principle (one of the principles of object-oriented design).
As an example, imagine a model that includes a general class called Shape and its subclasses Circle and Rectangle . Any of the Circle or Rectangle subclasses may include a
draw method, implemented in the base class Shape . However, the draw method will differ in every derived class. With polymorphism, the application can call the draw method from a Geometry object that is a Circle or Rectangle , and the appropriate method will be run depending on the actual object.The Advantages of Inheritance and Polymorphism
The advantages of the combined use of inheritance and polymorphism in C++ for the development of object-oriented systems include:1. Code Reusability: Classes can be reused without the need to rewrite them, as a class inherits from a specified class. This reduces redundancy and the effort required to write code.
2. Modularity: Inheritance and polymorphism allow systems to have new derived classes added or methods overridden without changes to the existing code. This increases modularity and scalability.
3. Versatility: Functions and methods can operate on different types of objects without needing to know their exact types, thanks to polymorphism. This enhances general-purpose coding and reduces restrictions on object types.
4. Reduced Complexity: Developers can modify a single class and expect those changes to propagate across the system. Sharing functionality reduces the likelihood of bugs caused by changes.
5. Increased Abstraction: Polymorphism and inheritance enable significant abstractions, making it easier to organize code logically and improve problem-solving.
Challenges and Considerations
Polymorphism and inheritance can be very helpful for developers, but they also present challenges. One problem stems from the close dependencies between classes. Whenever a base class is modified, all necessary derived classes must be updated as well. If not properly managed, this can create issues with maintenance.Another issue arises from multiple inheritance . When an ancestry includes several primary classes, confusion may occur if these classes contain functions with the same name. This can lead to unnecessary complications and make troubleshooting difficult, especially in larger systems.
