Calling copy constructor on void *

[Ramiraf]

I have a void * variable1, which is really a pointer to a class. I want
to copy the class itself (not just the pointer) onto another void *
variable2, using the variable1's class's copy constructor (I need to do
more than just a shallow copy). Is there any way to do this? Thanks in
advance.

Steve

[Victor Bazarov]

"Ramiraf" <bl**@blah.com> wrote...

I have a void * variable1, which is really a pointer to a class. I want
to copy the class itself (not just the pointer) onto another void *
variable2, using the variable1's class's copy constructor (I need to do
more than just a shallow copy). Is there any way to do this?

You would need to [statically] cast the pointer to the class
pointer and then do 'new'. Something like

void *variable1;
... // somehow 'variable1' now points to an instance
// of MyClass
void *variable2 =
new MyClass(*static_cast<MyClass*>(variable1));

(of course 'MyClass' needs to be defined here).

Victor

[John Dibling]

On Mon, 14 Jul 2003 10:12:16 -0700, Ramiraf <bl**@blah.com> wrote:

I have a void * variable1, which is really a pointer to a class. I want
to copy the class itself (not just the pointer) onto another void *
variable2, using the variable1's class's copy constructor (I need to do
more than just a shallow copy). Is there any way to do this? Thanks in
advance.

Steve

The key in doing a deep copy is performing a cast on your pointer to
get to the goodies in the class itself. You can use an old C-style
cast, or one of the new C++ casts, dynamic_cast, static_cast, etc.

Once youv'e casted to your class, you can call an operator= you have
implemented, or some funky deep-copy global method youv'e written;
whatever flavor poison you choose.

A bigger question is, why have you casted down your class pointer to
void*? There are very often good, valid reasons to do so. But using
void* as a generic pointer is usually (IMO) an over-used, cliche hack
around bad design.

</dib>

John Dibling
email: dib@substitute_my_full_last_name_here.com
Witty banter omitted for your protection