Re: Deriving from concrete types

From:

cbarron3@ix.netcom.com (Carl Barron)

Newsgroups:

comp.lang.c++.moderated

Date:

3 Jul 2006 07:13:14 -0400

Message-ID:

<1hhv311.13eqztvy0hqpiN%cbarron3@ix.netcom.com>

Lourens Veen <lourens@rainbowdesert.net> wrote:

Alan McKenney wrote:

struct KeywordData : public std::vector<Entry> { std::string
keyword; };

Interestingly, it's also a subtype in the Liskov sense of the word,
unlike a subclass which overrides a virtual member function and
changes the behaviour. I think this shows how Liskov-subtypes don't
make much sense in an OOP world, where objects can have very complex
behaviour. The only reason the concept does work here is because the
added part is plain old data.

   Std::string is not plain old datd:) If this is goimg to be used
in a context of runtime polymorphism, then the problem of no virtual
dtor() problem, still exists. If this is passed by reference/const
reference to
a routine that does not do tricks like store the addreess of the
reference, [the original KeywordData object] and then delete it
as an std::vector<...> *, all is fine.

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