virtual

• Methods can be virtual or non-virtual
• Constructors cannot be virtual
• What about destructors?

Example Classes

Usage

Run

Problem

• When using a Base pointer with a Derived object, the Derived destructor is not called
• Not only is the Derived destructor not called, the destructors for any fields/data members are also not called
• Why? The compiler uses static dispatch to set up a call to the destructor
• Solution: virtual Destructor

Virtual Destructor Classes

Virtual Destructor Usage

Virtual Destructor Run

Class Comparison

Run Comparison

Conclusion

• Any base class with a virtual method should have a virtual destructor
• If there is nothing to do in the destructor, use the default function specifier
• Default destructors are compiler generated and can be more efficient than user-created destructors
• Prefer to declare a default destructor in the include file, but if an issue, you can declare it in the implementation file, e.g., Base::~Base() = default;