How does polymorphism support dynamic binding in C++?

Dynamic binding in C++ is implemented by the virtual function mechanism, which allows determining which function or method to call at runtime: a virtual function is a member function that can be redefined by a derived class. When a virtual function is called, the compiler calls it indirectly through the vtable, which contains a table of addresses of all virtual function pointers of the class. When an object is created, the vtable pointer is stored in the object. When a virtual function is called, the compiler obtains the object's vtable pointer and uses it to determine the function to call.

How polymorphism supports dynamic binding in C++

Introduction

Dynamic binding is a key feature of polymorphism that allows determining which function or method to call at runtime. In C++, dynamic binding is implemented using the virtual function mechanism.

Virtual function mechanism

Virtual functions are member functions that can be redefined through derived classes. When a virtual function is called, the compiler does not call the function directly, but calls it indirectly through the vtable. The virtual table contains the address table of all virtual function pointers of the class.

When an object is created, the virtual table pointer is stored in the object. When a virtual function is called, the compiler obtains the object's vtable pointer and uses it to determine which function to call.

Code Example

class Base {
public:
    virtual void print() {
        cout << "Base class print" << endl;
    }
};

class Derived : public Base {
public:
    virtual void print() override {
        cout << "Derived class print" << endl;
    }
};

int main() {
    Base* base = new Derived;
    base->print(); // 动态绑定调用 Derived::print()
}

Practical Case

Dynamic binding is very useful in software development, it allows Modify the object's composition. A common example is a graphical user interface (GUI), where users can click different buttons or menu items to trigger different actions. By using dynamic binding, the GUI framework ensures that the correct handler is called when any button or menu item is clicked.

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