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Wed, 13 January 2010 11:17

mdelfede
Messages: 1307
Registered: September 2007

Ultimate Contributor

Having the need to create some class instances at runtime by class name (String, not type), I developed a small templatized class factory; it's the first step for the polymorphic xmlizer that I'll publish when ready.

Thank to Mirek who helped me with templates ! Smile

ClassFactory.h

#ifndef _ClassFactory_ClassFactory_h_
#define _ClassFactory_ClassFactory_h_

#include <Core/Core.h>
using namespace Upp;

template<class T> class WithFactory
{
	private:
		typedef One<T> (*CreateFunc)();
		typedef VectorMap<String, CreateFunc>mapType;
		static mapType &classMap() { static mapType cMap; return cMap; }
		template<class D> static One<T> __Create(void) { return One<T>((T *)new D); }
	public:
	
		template<class D> static void Register(const String &name) { classMap().Add(name, __Create<D>); }
		static One<T> Create(const String &className) { return classMap().Get(className)(); }
		static Vector<String> const &Classes(void) { return classMap().GetKeys(); }
};

#define REGISTERCLASS(type) \
	INITBLOCK { \
	type::Register<type>(#type); \
}
#endif

Sample usage:

#include "ClassFactory.h"

class Base : public WithFactory<Base>
{
	public:
		virtual String WhoAmI(void) { return "Base"; }
};

class Derived : public Base
{
	public:
		virtual String WhoAmI(void) { return "Derived"; }
};

REGISTERCLASS(Base);
REGISTERCLASS(Derived);

CONSOLE_APP_MAIN
{
	One<Base> p1 = Base::Create("Base");
	One<Base> p2 = Base::Create("Derived");
	
	Cerr() << "p1 is a '" << p1->WhoAmI() << "'\n";
	Cerr() << "p2 is a '" << p2->WhoAmI() << "'\n";
	
}

output :

p1 is a 'Base'
p2 is a 'Derived'

Ciao

Max

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