Re: Adding pointer to container

From:

Paavo Helde <nobody@ebi.ee>

Newsgroups:

comp.lang.c++

Date:

Sat, 14 Jun 2008 13:31:52 -0500

Message-ID:

<Xns9ABDDB06EA449nobodyebiee@216.196.97.131>

"Alf P. Steinbach" <alfps@start.no> kirjutas:

* Paavo Helde:

What about:

void function()
{
         m_elements.push_back(NULL);
         element*& ref = m_elements.back();
     ref = new DerivedElement;
}

If DerivedElement constructor throws, has already added nullpointer to
vector.

Yes, that's true. What I would do actually in this case, would be to use
the ScopeGuard from Andrei Alexandrescu. This is a case of glueing
together C-style interfaces (raw pointers!) and ScopeGuard comes quite
handy in such situations:

#include <ScopeGuard/ScopeGuard.h>

template <class T>
struct Delete {
    void operator()(T *t) const { delete t;}
};

void function()
{
     element* e = new DerivedElement;
     ScopeGuard guard = MakeGuard(Delete<element>(), e);
    m_elements.push_back(e);
     guard.Dismiss();
}

But this is only because I have the Delete template and ScopeGuard
includes already in place in the project anyway. std::auto_ptr would work
the same in this case (I suppose, never used myself) and would require
less code in this case.

Regards
Paavo