Can Polymorphism Exist Without Pointers or References?

Polymorphism Without Pointers and References: A Myth

Polymorphism is a fundamental aspect of object-oriented programming, enabling code to behave differently for objects of different subclasses. However, many developers ponder why polymorphism seems to require the use of pointers or references.

The Deceptive Role of Memory Allocation

"If you allocate memory on the heap, you have dynamic binding," one might think. While true, mere memory allocation does not suffice for polymorphism. Take the example:

Derived d;
Base* b = &d;

Here, d resides on the stack, yet polymorphism works seamlessly on b. This highlights that memory location is irrelevant for polymorphism.

Semantics: The Key to Polymorphism

The crucial factor lies in semantics. When you create a base class pointer or reference to a derived class instance, you effectively retain access to the derived class's methods. Consider:

Base c = Derived();

Although c is an instance of Base, it cannot exhibit polymorphic behavior because it stores a sliced version of the Derived object, losing its derived class identity.

Pointers vs. References

While both pointers and references establish indirection, pointers provide additional flexibility. They allow you to point to objects of any type, including both base and derived classes. In contrast, references can only bind to objects of a specific type, limiting their polymorphic capabilities.

Conclusion

Polymorphism without pointers or references is a misconception. The use of pointers and references ensures that the compiler maintains the necessary type information, allowing for dynamic resolution of method calls and true polymorphic behavior in your code.

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