// MT2Q4.cpp - build and destroy

#include <string>
#include <iostream>

class B
{
public:
  B() : pStr(new std::string("default")) {  
    std::cout << "\n  B constructed";
  }
  B(const B& b) : pStr(new std::string(*(b.pStr))) { 
    std::cout << "\n  B copied";
  }
  virtual ~B() { 
    delete pStr; 
    std::cout << "\n  B destroyed";
  }
  void take(std::string str)
  {
    delete pStr;
    pStr = new std::string(str);
  }
  virtual const std::string say() { 
    return *pStr; 
  }
  B& operator=(const B& b) { 
    if(&b == this) return *this;
    delete pStr;
    pStr = new std::string(*(b.pStr)); 
    std::cout << "\n  B assigned";
  }
private:
  std::string* pStr;
};

class D : public B
{
public:
  // B has correct copy, assignment, and destruction 
  // semantics so compiler generated operations for D
  // will be correct
  virtual const std::string say() { 
    std::string temp = "from derived class: ";
    return temp + static_cast<B*>(this)->B::say(); 
  }
};

int main()
{
  B b; 
  b.take("a string from client");
  std::cout << "\n  " << b.say();
  D d1;
  d1.take("another string from client");
  std::cout << "\n  " << d1.say();
  D d2 = D();
  std::cout << "\n  " << d2.say() << "\n\n";
  return 0;
}