Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!snorkelwacker.mit.edu!ira.uka.de!t500i0!fuchs
From: fuchs@t500i0.telematik.informatik.uni-karlsruhe.de (Harald Fuchs)
Newsgroups: comp.lang.c++
Subject: Re: assignment operator for dervired classes
Message-ID: <fuchs.672535189@t500i0>
Date: 24 Apr 91 23:19:49 GMT
References: <1991Apr23.153754.4582@netcom.COM>
Sender: news@ira.uka.de (USENET News System)
Organization: University of Karlsruhe, FRG
Lines: 58

aed@netcom.COM (Andrew Davidson) writes:

>I have been having trouble writing an assignment operator for a
>derived
>class. The problem is how do you initialize the the base class. The
>reading
>I have done to date suggest that that the assiginment operator for a
>derived
>class is written the same way the copy constructor is written.

>#include <s#ream.h>
>class X
>{
> public:

>  X(int i = 0)
>        {numX = i;}
>  X(const X &other)
>        {numX = other.numX;}
>  X& operator = (const X &other)
>        {
>          numX = other.numX;
>          return (*this);
>        }

>  void display() {cout << "numX = " << numX << " ";}

> private:
>  int numX;
>};

>class Y : public X
>{
> public:

>  Y(int i = 1) : X(i)
>        {numY = i;}
>  Y(const Y &other) : X(other)
>        {numY = other.numY;}

>  Y& operator = (const Y &other)
>        {
>/* 49 */          X(other);
>          numY = other.numY;
>          return(*this);
>        }

>  void display() {X::display(); cout << "numY = " << numY << "\n";}
> private:
>  int numY;
>};

Use the assignment operator of the base class.
Simply replace line 49 by
  X::operator= (other);
--

Harald Fuchs <fuchs@t500e0.telematik.informatik.uni-karlsruhe.de>