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////////////////////////////////////////////////////////////////////////////////
// The Loki Library
// Copyright (c) 2001 by Andrei Alexandrescu
// This code accompanies the book:
// Alexandrescu, Andrei. "Modern C++ Design: Generic Programming and Design
// Patterns Applied". Copyright (c) 2001. Addison-Wesley.
// Permission to use, copy, modify, distribute and sell this software for any
// purpose is hereby granted without fee, provided that the above copyright
// notice appear in all copies and that both that copyright notice and this
// permission notice appear in supporting documentation.
// The author or Addison-Wesley Longman make no representations about the
// suitability of this software for any purpose. It is provided "as is"
// without express or implied warranty.
////////////////////////////////////////////////////////////////////////////////
// Last update: June 20, 2001
#ifndef ABSTRACTFACTORY_INC_
#define ABSTRACTFACTORY_INC_
#include "Typelist.h"
#include "TypeManip.h"
#include "HierarchyGenerators.h"
#include <cassert>
namespace Loki
{
////////////////////////////////////////////////////////////////////////////////
// class template AbstractFactoryUnit
// The building block of an Abstract Factory
////////////////////////////////////////////////////////////////////////////////
template <class T>
class AbstractFactoryUnit
{
public:
virtual T* DoCreate(Type2Type<T>) = 0;
virtual ~AbstractFactoryUnit() {}
};
////////////////////////////////////////////////////////////////////////////////
// class template AbstractFactory
// Defines an Abstract Factory interface starting from a typelist
////////////////////////////////////////////////////////////////////////////////
template
<
class TList,
template <class> class Unit = AbstractFactoryUnit
>
class AbstractFactory : public GenScatterHierarchy<TList, Unit>
{
public:
typedef TList ProductList;
template <class T> T* Create()
{
Unit<T>& unit = *this;
return unit.DoCreate(Type2Type<T>());
}
};
////////////////////////////////////////////////////////////////////////////////
// class template OpNewFactoryUnit
// Creates an object by invoking the new operator
////////////////////////////////////////////////////////////////////////////////
template <class ConcreteProduct, class Base>
class OpNewFactoryUnit : public Base
{
typedef typename Base::ProductList BaseProductList;
protected:
typedef typename BaseProductList::Tail ProductList;
public:
typedef typename BaseProductList::Head AbstractProduct;
ConcreteProduct* DoCreate(Type2Type<AbstractProduct>)
{
return new ConcreteProduct;
}
};
////////////////////////////////////////////////////////////////////////////////
// class template PrototypeFactoryUnit
// Creates an object by cloning a prototype
// There is a difference between the implementation herein and the one described
// in the book: GetPrototype and SetPrototype use the helper friend
// functions DoGetPrototype and DoSetPrototype. The friend functions avoid
// name hiding issues. Plus, GetPrototype takes a reference to pointer
// instead of returning the pointer by value.
////////////////////////////////////////////////////////////////////////////////
template <class ConcreteProduct, class Base>
class PrototypeFactoryUnit : public Base
{
typedef typename Base::ProductList BaseProductList;
protected:
typedef typename BaseProductList::Tail ProductList;
public:
typedef typename BaseProductList::Head AbstractProduct;
PrototypeFactoryUnit(AbstractProduct* p = 0)
: pPrototype_(p)
{}
friend void DoGetPrototype(const PrototypeFactoryUnit& me,
AbstractProduct*& pPrototype)
{ pPrototype = me.pPrototype_; }
friend void DoSetPrototype(PrototypeFactoryUnit& me,
AbstractProduct* pObj)
{ me.pPrototype_ = pObj; }
template <class U>
void GetPrototype(AbstractProduct*& p)
{ return DoGetPrototype(*this, p); }
template <class U>
void SetPrototype(U* pObj)
{ DoSetPrototype(*this, pObj); }
AbstractProduct* DoCreate(Type2Type<AbstractProduct>)
{
assert(pPrototype_);
return pPrototype_->Clone();
}
private:
AbstractProduct* pPrototype_;
};
////////////////////////////////////////////////////////////////////////////////
// class template ConcreteFactory
// Implements an AbstractFactory interface
////////////////////////////////////////////////////////////////////////////////
template
<
class AbstractFact,
template <class, class> class Creator = OpNewFactoryUnit,
class TList = typename AbstractFact::ProductList
>
class ConcreteFactory
: public GenLinearHierarchy<
typename TL::Reverse<TList>::Result, Creator, AbstractFact>
{
public:
typedef typename AbstractFact::ProductList ProductList;
typedef TList ConcreteProductList;
};
} // namespace Loki
////////////////////////////////////////////////////////////////////////////////
// Change log:
// June 20, 2001: ported by Nick Thurn to gcc 2.95.3. Kudos, Nick!!!
////////////////////////////////////////////////////////////////////////////////
#endif // ABSTRACTFACTORY_INC_
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