Is there a way to disallow subclassing

[Mohammad]

Is there way to write a C++ class so that it cannot be subclassed?

 

[Ivan Vecerina]

Is there way to write a C++ class so that it cannot be subclassed?

There is, but it's unfortunately excessively complicated,
making it inconvenient to use.
It can be done by using virtual inheritance:

// class with private constructor and destructor
class Locker {
friend NotToBeSubclassed;
Locker() {};
~Locker() {};
};

class NotToBeSubclassed : virtual Locker
{
//... whatever
};

The trick is: a most-derived class must call the constructor
of all virtual base classes of its parents. But the private
constructor of 'Locker' is only accessible to the
'NotToBeSubclassed' class, which therefore cannot
be derived from.


hth, Ivan

 

[Domenico Andreoli]

There is, but it's unfortunately excessively complicated,
making it inconvenient to use.
It can be done by using virtual inheritance:

i'm not following you, why is required the virtual inheritance?

-----[ Domenico Andreoli, aka cavok
--[ http://filibusta.crema.unimi.it/~cavok/gpgkey.asc
---[ 3A0F 2F80 F79C 678A 8936 4FEE 0677 9033 A20E BC50

 

[Ivan Vecerina]

i'm not following you, why is required the virtual inheritance?

The most derived subclass is always responsible for initializing
a virtual base class. A non-virtual base class does not affect
subclasses.


Regards, Ivan

 

[Bobo]

Is there way to write a C++ class so that it cannot be subclassed?

It's easy: declare all your class constructors private!

 

[Thomas Wintschel]

(e-mail address removed) (Mohammad) wrote in message

It's easy: declare all your class constructors private!

of course then you can't construct one either. useful for singletons
though. or, you could have a static method that constructed them for you
and returned a pointer