#include <string>
#include <iostream>
class CustomString
{
	std::string data_;
public:
	CustomString() : data_("test string" ){};
	const char* data() const { return data_.c_str(); }
};
class External
{
	CustomString s_;
public:
	const CustomString some_interface() const { return s_; }
};
class CustomStringDecorator : public CustomString
{
public:
	CustomStringDecorator( const CustomString& cs ) : CustomString( cs ) {}
	operator const std::string() const { return std::string( data() ); }
	operator const char*() const { return data(); } 
};
class Internal
{
public:
	void some_interface( const CustomStringDecorator& csd )
	{
		std::cout << csd << std::endl;
	}
};
int main()
{
	External ex;
	Internal in;
	in.some_interface( ex.some_interface() );
}