Re: template-nested STL iterator question

From:
"Victor Bazarov" <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Wed, 10 May 2006 15:17:28 -0400
Message-ID:
<e3te89$mrg$1@news.datemas.de>
chriscorbell wrote:

I'm curious about what appears to be a restriction on using an STL
container inside a user-defined template, esp. using an iterator to
such a container. It's not clear to me if this is a general
template/language restriction, and STL iterator limitation, or if I'm
just going about it wrong.

I'm declaring a template which uses a std::map to store references to
the template type, e.g.

template template <typename T>
class MyClass
{
public:
 // ...
private:
 std::map<std::string, T*> m_objectMap;
};

This compiles fine. However if I have a declaration of an iterator to
this map in a method of my class, the compile fails, e.g.

template template <typename T>
class MyClass
{
public:
 T* Lookup(std::string)
 {
     T* pT = NULL;
     std::map<std::string, T*>::iterator iTptr = m_objectMap.find();


   typename std::map<...>::iterator iTptr = ...
   ^^^^^^^^

     if(iTptr != m_objectMap.end())
        pT = *iTptr;
     return pT;
 }
private:
 std::map<std::string, T*> m_objectMap;
};

Is there a correct way to accomplish this? If not, anyone know the
rationale?


Read the FAQ. Dependent names are described in the 'Templates' section.

The kludgy workaround I'm using is to use void * instead of T* for the
std::map and static-cast it.


That's a BAD IDEA(tm).

V
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