Description: Runtime polymorphism is a fundamental feature of object-oriented programming that allows a function or method to behave differently depending on the object that invokes it. In C++, this is primarily achieved through the use of pointers and references to base classes, along with the declaration of virtual methods. When a virtual method is called on an object, the compiler determines at runtime which version of the method should be executed, based on the actual type of the object, not the type of the pointer or reference. This ability to change the behavior of a method based on the specific object invoking it provides great flexibility and extensibility in software design. Runtime polymorphism is particularly useful in situations where different classes need to implement the same interface, allowing the code that uses these classes to be more generic and reusable. Additionally, it facilitates the implementation of design patterns such as the strategy pattern and the command pattern, where behavior can be modified at runtime without needing to change existing code. In summary, runtime polymorphism is a powerful tool that enhances code modularity and maintainability in object-oriented programming.
History: The concept of polymorphism in programming dates back to the early days of object-oriented programming in the 1960s, with languages like Simula. However, C++ popularized runtime polymorphism starting from its creation in 1983 by Bjarne Stroustrup, who introduced object-oriented programming features into a language that was originally a derivative of C. Since then, polymorphism has been a cornerstone in modern software development, enabling the creation of more flexible and maintainable systems.
Uses: Runtime polymorphism is widely used in software development to implement interfaces and abstract classes, allowing different classes to share the same interface and behave differently. This is particularly useful in applications that require extensibility, such as plugin systems, where new functionalities can be added without modifying existing code. It is also used in the development of frameworks and libraries, where a consistent API is sought to be used by different types of objects.
Examples: A practical example of runtime polymorphism in C++ is the use of a base class ‘Shape’ with a virtual method ‘draw’. Derived classes like ‘Circle’ and ‘Square’ can implement their own version of the ‘draw’ method. By using a pointer of type ‘Shape’ to point to an object of type ‘Circle’ or ‘Square’, the ‘draw’ method can be called, and the program will execute the corresponding implementation at runtime, depending on the actual type of the object. This allows the same code to handle different types of shapes efficiently.
