First blush

git-svn-id: svn://svn.code.sf.net/p/loki-lib/code/trunk@6 7ec92016-0320-0410-acc4-a06ded1c099a

Factory.h

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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-Welsey 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: February 19, 2001
+
+#ifndef FACTORY_INC_
+#define FACTORY_INC_
+
+#include "TypeInfo.h"
+#include "AssocVector.h"
+#include <exception>
+
+namespace Loki
+{
+
+////////////////////////////////////////////////////////////////////////////////
+// class template DefaultFactoryError
+// Manages the "Unknown Type" error in an object factory
+////////////////////////////////////////////////////////////////////////////////
+
+    template <typename IdentifierType, class AbstractProduct>
+    struct DefaultFactoryError
+    {
+        struct Exception : public std::exception
+        {
+            const char* what() const { return "Unknown Type"; }
+        };
+        
+        static AbstractProduct* OnUnknownType(IdentifierType)
+        {
+            throw Exception();
+        }
+    };
+
+////////////////////////////////////////////////////////////////////////////////
+// class template Factory
+// Implements a generic object factory
+////////////////////////////////////////////////////////////////////////////////
+
+    template
+    <
+        class AbstractProduct, 
+        typename IdentifierType,
+        typename ProductCreator = AbstractProduct* (*)(),
+        template<typename, class>
+            class FactoryErrorPolicy = DefaultFactoryError
+    >
+    class Factory 
+        : public FactoryErrorPolicy<IdentifierType, AbstractProduct>
+    {
+    public:
+        bool Register(const IdentifierType& id, ProductCreator creator)
+        {
+            return associations_.insert(
+                IdToProductMap::value_type(id, creator)).second;
+        }
+        
+        bool Unregister(const IdentifierType& id)
+        {
+            return associations_.erase(id) == 1;
+        }
+        
+        AbstractProduct* CreateObject(const IdentifierType& id)
+        {
+            typename IdToProductMap::const_iterator i = associations_.find(id);
+            if (i != associations_.end())
+            {
+                return (i->second)();
+            }
+            return OnUnknownType(id);
+        }
+        
+    private:
+        typedef AssocVector<IdentifierType, ProductCreator> IdToProductMap;
+        IdToProductMap associations_;
+    };
+
+////////////////////////////////////////////////////////////////////////////////
+// class template CloneFactory
+// Implements a generic cloning factory
+////////////////////////////////////////////////////////////////////////////////
+
+    template
+    <
+        class AbstractProduct, 
+        class ProductCreator = 
+            AbstractProduct* (*)(const AbstractProduct*),
+        template<typename, class>
+            class FactoryErrorPolicy = DefaultFactoryError
+    >
+    class CloneFactory
+        : public FactoryErrorPolicy<TypeInfo, AbstractProduct>
+    {
+    public:
+        bool Register(const TypeInfo& ti, ProductCreator creator)
+        {
+            return associations_.insert(
+                IdToProductMap::value_type(ti, creator)).second;
+        }
+        
+        bool Unregister(const TypeInfo& id)
+        {
+            return associations_.erase(id) == 1;
+        }
+        
+        AbstractProduct* CreateObject(const AbstractProduct* model)
+        {
+            if (model == 0) return 0;
+            
+            typename IdToProductMap::const_iterator i = 
+                associations_.find(typeid(*model));
+            if (i != associations_.end())
+            {
+                return (i->second)(model);
+            }
+            return OnUnknownType(typeid(*model));
+        }
+        
+    private:
+        typedef AssocVector<TypeInfo, ProductCreator> IdToProductMap;
+        IdToProductMap associations_;
+    };
+} // namespace Loki
+
+#endif // FACTORY_INC_