Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!apple!netcom!sjsumcs!horstman
From: horstman@mathcs.sjsu.edu (Cay Horstmann)
Newsgroups: comp.lang.c++
Subject: Re: Constructor question
Message-ID: <1991Apr5.035053.27973@mathcs.sjsu.edu>
Date: 5 Apr 91 03:50:53 GMT
References: <1991Apr2.110623.22219@and.cs.liv.ac.uk> <fuchs.670695206@t500e0>
Organization: San Jose State University - Math/CS Dept.
Lines: 39

In article <fuchs.670695206@t500e0> fuchs@t500e0.telematik.informatik.uni-karlsruhe.de (Harald Fuchs) writes:
>markr@and.cs.liv.ac.uk writes:
>
>>Can I call one constructor to class X explicitly from within another
>>constructor to class X ?
>
>>Example: constructor X::X( int i ) performs a lot of initialisation that needs
>>to be done at the start of X::X( char *c ) too.  Can I write:
>
>>X::X( char *c ) {
>>	X( 5 );
>>	// rest of stuff
>
>
>>?  Or maybe something similar with different syntax?
>
>>Apologies for turning the group into a tutorial session, but I can't find any
>>reference to this in my C++ books.
>
>That's because there is no such thing. 

That isn't quite true. One could presumably call the constructor
explicitly with the placement syntax:

	new(this) X(5);

I am NOT going to advocate this style. In fact, it seems the totally WRONG
thing to do since it can be brokem by redefining X::operator new( size_t, void* ).


>When I have to do lots of
>common initialization, I put it into a private member function
>(e.g. void init ();) and call this function from the constructors.
>Unfortunately, this won't work if you have to initialize constant or
>reference data members. IMHO a hole in the language.
>
Good point! 

Cay