manage polymorphic class persistency

From:
"Fei Liu" <fei.liu@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
28 Jun 2006 06:33:52 -0400
Message-ID:
<1151416224.997630.76070@y41g2000cwy.googlegroups.com>
Creational patterns such as prototype, factory method, abstract factory
often require that object creation in a somewhat hardcoded way. For
example, in creating a system where a hierarchy of objects need to be
saved and restored to/from persistent storage:

Shape
|========|========|
Circle====Square===Triangle

A bruteforce approach to restore from persistent storage would be
something like this

class ShapeFactory{
public:
    static Shape * CreateShape(char tag){
          switch(tag){
               'C': return Circle.CreateCircle();
               'S': return Square.CreateSquare();
          }
     }
};

class Circle{
    public:
        static Circle * CreateCircle(){ return new Circle(); }
};

What's shown here is a factory method design pattern. My question is if
there is a better (or standard) way to solve this problem. Thank you!

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