NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/comp/lang/cplus/19813

Text File | 1993-01-24 | 1.6 KB | 53 lines

Newsgroups: comp.lang.c++
Path: sparky!uunet!taumet!steve
From: [e-mail] (Steve Clamage)
Subject: Re: Friend ..Overload Assignment opertr ..
Message-ID: <[e-mail]>
Organization: TauMetric Corporation
References: <[e-mail]>
Date: Sat, 23 Jan 1993 20:04:32 GMT
Lines: 42

[e-mail] (Srinivasa Rao K) writes:


>       I am writing a "string"  class which i should be able to use like

>       string str1;
>       str1 = "Hello world" ;

>       But We canot use a friend to overload the assignment oprator.

A String class will usually contain pointers, and so should have
a user-defined assignment operator (which must be a member function,
as you note) and copy constructor.  If not, you will be vary likely to
have bizarre program crashes.  See the book "Effective C++" by Scott
Meyers for a detailed discussion.

If you add a String constructor which takes a const char* parameter,
you don't have to do anything else.  It is hard to imagine a String
class without such a constructor.  Example:

    class String {
    public:
        String();            // default constructor (optional)
        String(const char*);
        String(const String&);    // copy constructor
        String& operator=(const String &); // assignment operator
        ...
    };

    String s;
    s = "Hello";

The string "Hello" will automatically be converted to a String by the
constructor, then assigned via the assigment operator.  The code is
evaluated as if you had written
    s.operator=( String("Hello") );

The copy constructor is not relevent for this example, but you should
have one anyway.
--

Steve Clamage, TauMetric Corp, [e-mail]