Why Are Pointers/References Essential for Polymorphism?

Polymorphism: The Need for Pointers/References

Polymorphism, a fundamental concept in object-oriented programming, allows objects of different classes to be treated as if they belong to a common superclass. While it may seem intuitive that allocating memory on the heap would suffice for dynamic binding, the absence of pointers or references fundamentally hinders polymorphism.

To understand why, consider the following example:

Derived d;
Base* b = &d;

In this scenario, d resides on the stack, yet polymorphism remains functional for b. This is because b retains the necessary information to locate the derived class instance.

On the other hand, without a base class pointer or reference, polymorphism cannot operate. Consider:

Base c = Derived();

Due to slicing, the c object is recognized as a Base rather than a Derived object. While polymorphism technically works, the derived class object is essentially lost.

Finally, in the code below:

Base* c = new Derived();

c simply points to a memory location, potentially containing a Base or Derived object. Dynamic binding is still possible for virtual method calls because the caller is unaware of the specific class.

Therefore, the use of pointers or references is indispensable for polymorphism as they:

• Allow access to objects' full functionality
• Provide a mechanism to retrieve the correct derived class instance
• Ensure dynamic binding, enabling polymorphism to be effective

The above is the detailed content of Why Are Pointers/References Essential for Polymorphism?. For more information, please follow other related articles on the PHP Chinese website!