Re: Problem with function not being visible

From:
"Victor Bazarov" <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Tue, 24 Apr 2007 15:02:15 -0400
Message-ID:
<f0lk7p$7cl$1@news.datemas.de>
chris@foobar.com wrote:

Guys, I have the following piece of code. Could you please help me
understand why b.ToString( ) cannot be called while b.foo( ) can?
When I compile I get (gcc, but visual studio gives the same pretty
much). Thanks


Binding a reference to non-const to a temporary is prohibited.

$ g++ -Wall foo.cpp
foo.cpp: In function `int main(int, char**)':
foo.cpp:21: error: no matching function for call to `Bar::ToString()'
foo.cpp:14: note: candidates are: virtual std::string
Bar::ToString(std::string&) const

#include <stdlib.h>
#include <string>
using namespace std;

template <typename _T> class Foo {


You should avoid using names that begin with an underscore and
a capital letter. They are reserved by the implementation.

public:
 virtual std::string ToString (std::string& pfx) const = 0;
 std::string ToString ( ) const { return(ToString(std::string( ))); }


Are you trying to call the virtual function (declared just before) here?
You cannot bind the temporary to a refernece to non-const. You have to
change the body to be

   { std::string s; return ToString(s); }

 virtual void* _foo ( ) const = 0;
 void* foo( ) const { return (_foo( )); }
};

class Bar: public Foo<int> {
public:
 std::string ToString (std::string& pfx) const
                        { return (std::string("test")); }
void* _foo ( ) const { return(NULL); }


I've reformatted it a bit, just to fit them on a line.

};

int main (int argc, char **argv) {
 Bar b;
 b.foo( );
 b.ToString( );
 return (0);
}


V
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