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From: huw@siesoft.co.uk (Huw Roberts)
Newsgroups: comp.lang.c++
Subject: Virtual creation of class instances? (help)
Summary: I want to create instances of an unknown class at run time.
Keywords: parse virtual creation
Message-ID: <1990Sep10.182039.8327@siesoft.co.uk>
Date: 10 Sep 90 18:20:39 GMT
Sender: usenet@siesoft.co.uk (NNTP Poster)
Distribution: comp
Organization: Siemens System Developement Group, Reading, UK
Lines: 30


I have a file full of lines containing orders for a program to execute.
I want each line in the file to correspond to an instance of a class,
the exact class being determined by the content of the line.

So, for example, if the file contained:
    order1(parameters)
    order2(parameters)
    order1(parameters)

I would want the program to create two instances of class "Order1" and
one instance of class "Order2".
Both Order1 and Order2 will be classes derived from a base class "Order".
Ideally, the information about which class is generated from each line would be
stored in a table somehow.  But how do I do it?  I don't want something like
    switch(type)
    {
	case order1:  object = new Order1();
		      break;
	case order2:  object = new Order2();
		      break;
    }
and I would rather not have functions in a table, each of which generates
an instance of the class (this is what I would do in C) unless they were
member functions of the order classes.

Help

Thanks,   Huw.
P.S.  Please post me directly 'cos I don't normally read this group.