include/Factory.h

   1 /***************************************************************************
   2  *   This file is part of KWorship.                                        *
   3  *   Copyright 2008 James Hogan <james@albanarts.com>                      *
   4  *                                                                         *
   5  *   KWorship is free software: you can redistribute it and/or modify      *
   6  *   it under the terms of the GNU General Public License as published by  *
   7  *   the Free Software Foundation, either version 2 of the License, or     *
   8  *   (at your option) any later version.                                   *
   9  *                                                                         *
  10  *   KWorship is distributed in the hope that it will be useful,           *
  11  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  12  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  13  *   GNU General Public License for more details.                          *
  14  *                                                                         *
  15  *   You should have received a copy of the GNU General Public License     *
  16  *   along with KWorship.  If not, write to the Free Software Foundation,  *
  17  *   Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.   *
  18  ***************************************************************************/
  19
  20 #ifndef _Factory_h_
  21 #define _Factory_h_
  22
  23 /**
  24  * @file Factory.h
  25  * @brief A generic object factory.
  26  * @author James Hogan <james@albanarts.com>
  27  */
  28
  29 #include "functionInfo.h"
  30
  31 #include <QHash>
  32
  33 /** A generic object factory.
  34  * Types can be registered to this class and then constructed using a key.
  35  */
  36 template <typename KEY, typename BASE, typename TUPLE>
  37 class Factory
  38 {
  39   public:
  40
  41     /*
  42      * Constructors + destructor
  43      */
  44
  45     /// Default constructor.
  46     Factory()
  47     : m_constructors()
  48     {
  49     }
  50
  51     /// Destructor.
  52     ~Factory()
  53     {
  54       foreach (BaseConstructor* constructor, m_constructors)
  55       {
  56         delete constructor;
  57       }
  58     }
  59
  60     /*
  61      * Type registration
  62      */
  63
  64     /** Add a type to the factory.
  65      * @param T Type to add.
  66      * @param key Identifier used to construct.
  67      */
  68     template <typename T>
  69     bool addType(const KEY& key)
  70     {
  71       typename ConstructorHash::const_iterator it = m_constructors.constFind(key);
  72       if (it == m_constructors.constEnd())
  73       {
  74         m_constructors[key] = new Constructor<T>();
  75         return true;
  76       }
  77       return false;
  78     }
  79
  80     /*
  81      * Construction
  82      */
  83
  84     BASE* construct(KEY key)
  85     {
  86       return constructFromPack(key, TUPLE::pack());
  87     }
  88     template <typename Param1>
  89     BASE* construct(KEY key, const Param1& param1)
  90     {
  91       return constructFromPack(key, TUPLE::pack(param1));
  92     }
  93     template <typename Param1, typename Param2>
  94     BASE* construct(KEY key, const Param1& param1, const Param2& param2)
  95     {
  96       return constructFromPack(key, TUPLE::pack(param1, param2));
  97     }
  98
  99     /** Construct a type using a pack of arguments.
 100      * @param key identifier of type to construct.
 101      * @param pack pack of arguments.
 102      */
 103     BASE* constructFromPack(KEY key, const typename TUPLE::Pack& pack)
 104     {
 105       typename ConstructorHash::const_iterator it = m_constructors.constFind(key);
 106       if (it != m_constructors.constEnd())
 107       {
 108         return (*it)->construct(pack);
 109       }
 110       else
 111       {
 112         return 0;
 113       }
 114     }
 115
 116   private:
 117
 118     /*
 119      * Types
 120      */
 121
 122     /// Base constructor class.
 123     class BaseConstructor
 124     {
 125       public:
 126         virtual ~BaseConstructor() {}
 127         /// Construct an instance of a dervied type.
 128         virtual BASE* construct(const typename TUPLE::Pack& pack) const = 0;
 129     };
 130
 131     /** Type specific generic constructor.
 132      * @param TYPE Type to construct.
 133      */
 134     template <typename TYPE>
 135     class Constructor : public BaseConstructor
 136     {
 137       public:
 138         virtual ~Constructor() {}
 139         virtual BASE* construct(const typename TUPLE::Pack& pack) const
 140         {
 141           return pack.template construct<TYPE>();
 142         }
 143     };
 144
 145     /// Hash of keys to constructors.
 146     typedef QHash<KEY, BaseConstructor*> ConstructorHash;
 147
 148     /*
 149      * Variables
 150      */
 151
 152     /// Constructors by key.
 153     ConstructorHash m_constructors;
 154 };
 155
 156 #endif // _Factory_h_
 157