Re: Pure virtual destructor

On 2007-12-25 23:07:50 -0600, johanatan <johanatan@gmail.com> said:


A pure virtual destructor serves a different need than the typical pure
virtual function. The syntax exists to allow you to define a virtual
destructor, and still have the class treated as abstract. This is
useful in certain cases where you want to define an abstract interface
or tag class through which a derived object can be deleted. Without the
=0 in the destructor, you'd have to define another pure virtual
function in order to make the base class abstract.

For instance,

class Tag
{
public:
    virtual ~Tag() = 0;
};
Tag::~Tag() {}

class Foo: public Tag
{
public:
    Foo();
    virtual ~Foo();
};
Foo::Foo() {}

int main()
{
    //Tag t; // <-- error, abstract.
    Tag* pt = new Foo(); // <-- ok.
    delete pt; // <-- ok, Foo::~Foo is called.
}

-dr