// A2.1.cpp : Defines the entry point for the console application.
//
// Given the declarations:
//
// class D : public B { … private: std::string s; std::istream &is; }
//
// Can you write an assignment operator for this class?  If not, why not? 
// How would you support both a string and an input stream as data members 
// in a way that allows assignment?  Please write an assignment operator 
// for this D class.  You may assume that the only data members of D are 
// those shown.

#include "stdafx.h"
#include <iostream>
#include <string>

class B {};

class D : public B {
public:
  D() : B(), s("default string"), pIstream(NULL) {}
  D(const D &d) : B(d), s(d.s), pIstream(d.pIstream) {}
  void setStream(std::istream& in) { pIstream = &in; }
  void setString(const std::string& str) { s = str; }
  bool read();
  void write(std::ostream& out) { out << s.c_str(); }
  D& operator=(const D& d);
private:
  std::string s;
  std::istream* pIstream;
};

//// answer /////////////////////
D& D::operator =(const D& d) {
  if(this == &d) return *this;
  (B&)(*this) = d;
  pIstream = d.pIstream;
  s = d.s;
  return *this;
}
/////////////////////////////////

bool D::read() {
  if(!pIstream->good())
    return false;
  std::string line;
  std::getline(*pIstream,line);
  if(line.size() == 0)
    return false;
  s += line;
  s += '\n';
  return (pIstream->good());
}

int _tmain(int argc, _TCHAR* argv[])
{
  std::cout << "\n  Exam A2 - Question #1 "
            << "\n =======================\n";

  D d1;
  d1.setStream(std::cin);
  d1.setString("first object:\n");
  D d2;
  d2 = d1;
  d2.write(std::cout);
  d2.setString("");

  bool ok;
  do {
    std::cout << "\nplease enter some text from keyboard, enter to quit:\n";
    ok = d2.read();  
    std::cout << "\n---- writing what was read from keyboard ----\n";
    d2.write(std::cout);
    std::cout << std::endl;
  } while(ok);

  std::cout << "\n\n";
  return 0;
}