Re: Problem with static downcast of base type to derived type

From:
acehreli@gmail.com
Newsgroups:
comp.lang.c++
Date:
Wed, 2 Jul 2008 14:06:33 -0700 (PDT)
Message-ID:
<31d6e361-5649-4171-ab5e-eb5f190048b8@w1g2000prd.googlegroups.com>
On Jul 2, 1:31 pm, Erik Wikstr=F6m <Erik-wikst...@telia.com> wrote:

On 2008-07-02 21:13, Dom Jackson wrote:

Besides that, when casting from base to derived you should use
dynamic_cast and check if the cast succeeded (in which case the returned
pointer will be non-0). If you do that in your code you will notice that
you will always get a 0-pointer.


Of course the OP must have at least one virtual function in Base for
dynamic_cast to work.

A cast from pointer to base class to a
pointer to derived is only allowed if the object pointed to is of type
derived.


True.

You can always cast from pointer to derived to pointer to base using
static_cast, but when going the other way you shall use dynamic_cast.


static_cast is fine even for downcasting, as long as the target type
is correct. static_cast is for when the destination type is known at
compile time.

Did you mean that static_cast can not be used in polymorphic
hierarchies? If so, it's news to me and I don't have the standard
handy to check. :)

Ali

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