Re: Problem with function not being visible

From:

Andre Kostur <nntpspam@kostur.net>

Newsgroups:

comp.lang.c++

Date:

Tue, 24 Apr 2007 19:36:22 +0000 (UTC)

Message-ID:

<Xns991C80A9929A1nntpspamkosutrnet@209.135.99.21>

chris@foobar.com wrote in
news:462e51ab$0$1651$c3e8da3@news.astraweb.com:

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

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

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

ToString no longer exists taking no parameters when called on a Bar. As
soon as you declared std::string ToString(std::string& pfx) in your derived
class, it will hide all other declarations of ToString. If you still want
to use the no-parameter form of ToString, you'll have to add a using Foo
<int>::ToString into your Bar class.

In addition to Victor's comment that you may not bind a temporary to a non-
const reference. But that's a different issue.