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qdbtsingleton.h

#ifndef _QDBTSINGLETON_H
#define _QDBTSINGLETON_H

#include <qmap.h>
#include <qstring.h>
#include <qstringlist.h>

#include <qdbt/qdbtglobal.h>

class QdbtBaseTabular;

class QDBT_EXPORT QdbtSingletonObject
{
public:
  virtual ~QdbtSingletonObject();

protected:

  QdbtSingletonObject()
    {
    }
};

class QDBT_EXPORT QdbtSingleton
{
  class keyObject
  {
  public:
    keyObject() :
      _object( 0 ),
      _index( 0 )
      {
      }
    keyObject( const keyObject &obj ) :
      // This is one of the rare reasonable occurances, where a pointer is
      // meant to be simply copied!
      _object( obj._object ),
      _index( obj._index )
      {
      }
    keyObject & operator=( const keyObject &obj )
      {
        // This is one of the rare reasonable occurances, where a pointer is
        // meant to be simply copied!
        _object = obj._object;
        _index  = obj._index;
        return *this;
      }

    bool operator<( const keyObject &k ) const
      {
        return ( _object == k._object ?
                 _index < k._index :
                 _object < k._object );
      }

    const QdbtBaseTabular *_object;
    int                    _index;
  };

  static QStringList                              _indexLookup;
  static QMap< keyObject, QdbtSingletonObject * > _lookup;

public:
  static QdbtSingletonObject *checkPointer( const QdbtBaseTabular *object,
                                            const char *role );
  template < class T > static T checkPointer(
    const QdbtBaseTabular *object, const char *role )
    {
      T t = 0;
      try
      {
        t = dynamic_cast< T >( checkPointer( object, role ) );
      }
      catch ( ... )
      {
      }
      return t;
    }
  template < class T > static void checkPointer(
    const QdbtBaseTabular *object, const char *role, T result )
    {
      result = 0;
      try
      {
        result = dynamic_cast< T >( checkPointer( object, role ) );
      }
      catch ( ... )
      {
      }
    }
  static void setPointer( const QdbtBaseTabular *object,
                          const char *role,
                          QdbtSingletonObject *objectPointer );
  static void removePointers( const QdbtBaseTabular *object );
  static void removePointer( const QdbtSingletonObject *objectPointer );
  static void dump();
};

#endif

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