C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  friends and class templates          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message TheFerryman Guest Posted: Thu Mar 04, 2004 3:55 pm    Post subject: friends and class templates The easiest way to describe this is with some code. In the following, I would like the Thingalator::Func method to be able to access the private member variable Thing::m_TList. Is it possible to make Thingalator a friend of Thing? If so how? Many thanks //--------------------------------------------------------------------- #include <list> template <class T> class Thing { public: typedef std::list<T> TList; private: TList m_TList; public: Thing(){} }; template <class thing_type> class Thingalator { thing_type m_Thing; public: void Func() { thing_type::TList local = m_Thing.m_TList; } }; int main() { Thingalator<Thing t; t.Func(); return 0; } //--------------------------------------------------------------------- Back to top Leor Zolman Guest Posted: Thu Mar 04, 2004 4:09 pm    Post subject: Re: friends and class templates On Thu, 04 Mar 2004 15:55:47 +0000, TheFerryman <ferry (AT) onthenet (DOT) com> wrote: Quote: The easiest way to describe this is with some code. In the following, I would like the Thingalator::Func method to be able to access the private member variable Thing::m_TList. Is it possible to make Thingalator a friend of Thing? If so how? Many thanks //--------------------------------------------------------------------- #include <list Put this here: template (inform the compiler there's going to be a class template Thingalator) Quote: template <class T class Thing { and now make that class a friend: friend class Thingalator; Quote: public: typedef std::list<T> TList; [snip] -leor Leor Zolman BD Software [email]leor (AT) bdsoft (DOT) com[/email] www.bdsoft.com -- On-Site Training in C/C++, Java, Perl & Unix C++ users: Download BD Software's free STL Error Message Decryptor at www.bdsoft.com/tools/stlfilt.html Back to top Leor Zolman Guest Posted: Thu Mar 04, 2004 4:22 pm    Post subject: Re: friends and class templates On Thu, 04 Mar 2004 16:09:38 GMT, Leor Zolman <leor (AT) bdsoft (DOT) com> wrote: Quote: template <class T class Thing { and now make that class a friend: friend class Thingalator; Sorry, that may have been more restrictive than you needed. This works more generally: friend class Thingalator; -leor Leor Zolman BD Software [email]leor (AT) bdsoft (DOT) com[/email] www.bdsoft.com -- On-Site Training in C/C++, Java, Perl & Unix C++ users: Download BD Software's free STL Error Message Decryptor at www.bdsoft.com/tools/stlfilt.html Back to top TheFerryman Guest Posted: Thu Mar 04, 2004 4:32 pm    Post subject: Re: friends and class templates On Thu, 04 Mar 2004 16:22:04 GMT, Leor Zolman <leor (AT) bdsoft (DOT) com> wrote: Quote: On Thu, 04 Mar 2004 16:09:38 GMT, Leor Zolman <leor (AT) bdsoft (DOT) com> wrote: template <class T class Thing { and now make that class a friend: friend class Thingalator; Thanks leor. This works. Quote: Sorry, that may have been more restrictive than you needed. This works more generally: friend class Thingalator; But this more general case doesn't. I'm using MSVC6. Do you think that's the reason? I'd prefer to use this form because my Thingalator class may use any class derived from a Thing. Back to top Leor Zolman Guest Posted: Thu Mar 04, 2004 5:08 pm    Post subject: Re: friends and class templates On Thu, 04 Mar 2004 16:32:39 +0000, TheFerryman <ferry (AT) onthenet (DOT) com> wrote: Quote: On Thu, 04 Mar 2004 16:22:04 GMT, Leor Zolman <leor (AT) bdsoft (DOT) com> wrote: On Thu, 04 Mar 2004 16:09:38 GMT, Leor Zolman <leor (AT) bdsoft (DOT) com> wrote: template <class T class Thing { and now make that class a friend: friend class Thingalator; Thanks leor. This works. Sorry, that may have been more restrictive than you needed. This works more generally: friend class Thingalator; But this more general case doesn't. I'm using MSVC6. Do you think that's the reason? Yes and no. I'm not sure that last way I wrote it is actually even legal; it just happened to compile OK with VC7.1 in its default mode. Rewriting it like this: template<typename> friend class Thingalator; works with VC71, Comeau and CodeWarrior, so I suspect that's more standard-compliant. But that doesn't help you much in the case of pre-v7.1 MSVC...I can only think of ugly hack solutions that would generalize this for VC6 (ones you'd probably resort to yourself if you had to), so I won't post them. Perhaps someone else knows of an elegant way to deal with this under VC6. Or perhaps you can use this as a justification to upgrade to 7.1 (a good idea if you're planning to do Stupid Template Tricks of any significant variety...) -leor Quote: I'd prefer to use this form because my Thingalator class may use any class derived from a Thing. Leor Zolman BD Software [email]leor (AT) bdsoft (DOT) com[/email] www.bdsoft.com -- On-Site Training in C/C++, Java, Perl & Unix C++ users: Download BD Software's free STL Error Message Decryptor at www.bdsoft.com/tools/stlfilt.html Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.