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//
// MetaObject.h
//
// Library: Foundation
// Package: SharedLibrary
// Module: ClassLoader
//
// Definition of the MetaObject class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
#ifndef Foundation_MetaObject_INCLUDED
#define Foundation_MetaObject_INCLUDED
#include "Poco/Foundation.h"
#include "Poco/Exception.h"
#include "Poco/SingletonHolder.h"
#include <set>
namespace Poco {
template <class B>
class AbstractMetaObject
/// A MetaObject stores some information
/// about a C++ class. The MetaObject class
/// is used by the Manifest class.
/// AbstractMetaObject is a common base class
/// for all MetaObject in a rooted class hierarchy.
/// A MetaObject can also be used as an object
/// factory for its class.
{
public:
AbstractMetaObject(const char* pName): _name(pName)
{
}
virtual ~AbstractMetaObject()
{
for (typename ObjectSet::iterator it = _deleteSet.begin(); it != _deleteSet.end(); ++it)
{
delete *it;
}
}
const char* name() const
{
return _name;
}
virtual B* create() const = 0;
/// Create a new instance of a class.
/// Cannot be used for singletons.
virtual B& instance() const = 0;
/// Returns a reference to the only instance
/// of the class. Used for singletons only.
virtual bool canCreate() const = 0;
/// Returns true iff the create method can be used
/// to create instances of the class.
/// Returns false if the class is a singleton.
virtual void destroy(B* pObject) const
/// If pObject was owned by meta object, the
/// ownership of the deleted object is removed
/// and the object is deleted.
{
typename ObjectSet::iterator it = _deleteSet.find(pObject);
if (it != _deleteSet.end())
{
_deleteSet.erase(pObject);
delete pObject;
}
}
B* autoDelete(B* pObject) const
/// Give ownership of pObject to the meta object.
/// The meta object will delete all objects it owns
/// when it is destroyed.
///
/// Returns pObject.
{
if (this->canCreate()) // guard against singleton
{
poco_check_ptr (pObject);
_deleteSet.insert(pObject);
}
else throw InvalidAccessException("Cannot take ownership of", this->name());
return pObject;
}
virtual bool isAutoDelete(B* pObject) const
/// Returns true if the object is owned
/// by meta object.
///
/// Overloaded in MetaSingleton - returns true
/// if the class is a singleton.
{
return _deleteSet.find(pObject) != _deleteSet.end();
}
private:
AbstractMetaObject();
AbstractMetaObject(const AbstractMetaObject&);
AbstractMetaObject& operator = (const AbstractMetaObject&);
typedef std::set<B*> ObjectSet;
const char* _name;
mutable ObjectSet _deleteSet;
};
template <class C, class B>
class MetaObject: public AbstractMetaObject<B>
/// A MetaObject stores some information
/// about a C++ class. The MetaObject class
/// is used by the Manifest class.
/// A MetaObject can also be used as an object
/// factory for its class.
{
public:
MetaObject(const char* name): AbstractMetaObject<B>(name)
{
}
~MetaObject()
{
}
B* create() const
{
return new C;
}
B& instance() const
{
throw InvalidAccessException("Not a singleton. Use create() to create instances of", this->name());
}
bool canCreate() const
{
return true;
}
};
template <class C, class B>
class MetaSingleton: public AbstractMetaObject<B>
/// A SingletonMetaObject disables the create() method
/// and instead offers an instance() method to access
/// the single instance of its class.
{
public:
MetaSingleton(const char* name): AbstractMetaObject<B>(name)
{
}
~MetaSingleton()
{
}
B* create() const
{
throw InvalidAccessException("Cannot create instances of a singleton class. Use instance() to obtain a", this->name());
}
bool canCreate() const
{
return false;
}
B& instance() const
{
return *_object.get();
}
bool isAutoDelete(B* /*pObject*/) const
{
return true;
}
private:
mutable SingletonHolder<C> _object;
};
} // namespace Poco
#endif // Foundation_MetaObject_INCLUDED
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