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/*
Copyright (C) 2014 Carl Hetherington <cth@carlh.net>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/** @file src/ref.h
* @brief Ref class.
*/
#ifndef LIBDCP_REF_H
#define LIBDCP_REF_H
#include "exceptions.h"
#include "object.h"
#include "util.h"
#include <boost/shared_ptr.hpp>
#include <string>
namespace dcp {
/** @class Ref
* @brief A reference to an object which is identified by a universally-unique identifier (UUID).
*
* This class is a `pointer' to a thing. It will always know the
* UUID of the thing, and it may have a shared_ptr to the C++ object
* which represents the thing.
*
* If the Ref does not have a shared_ptr it may be given one by
* calling resolve() with a list of objects. The shared_ptr will be
* set up using any object on the list which has a matching ID.
*/
template<class T>
class Ref
{
public:
/** Initialise a Ref with an ID but no shared_ptr */
Ref (std::string id)
: _id (id)
{}
/** Initialise a Ref with a shared_ptr to an object */
Ref (boost::shared_ptr<T> object)
: _id (object->id ())
, _object (object)
{}
/** Set the ID of this Ref */
void set_id (std::string id)
{
_id = id;
}
/** Look through a list of objects and copy a shared_ptr to any object
* which matches the ID of this one.
*/
void resolve (std::list<boost::shared_ptr<Object> > objects)
{
typename std::list<boost::shared_ptr<Object> >::iterator i = objects.begin();
while (i != objects.end() && !ids_equal ((*i)->id(), _id)) {
++i;
}
if (i != objects.end ()) {
_object = boost::dynamic_pointer_cast<T> (*i);
}
}
/** @return the ID of the thing that we are pointing to */
std::string id () const {
return _id;
}
/** @return a shared_ptr to the thing; an UnresolvedRefError is thrown
* if the shared_ptr is not known.
*/
boost::shared_ptr<T> object () const {
if (!_object) {
throw UnresolvedRefError (_id);
}
return _object;
}
/** operator-> to access the shared_ptr; an UnresolvedRefError is thrown
* if the shared_ptr is not known.
*/
T * operator->() const {
if (!_object) {
throw UnresolvedRefError (_id);
}
return _object.get ();
}
/** @return true if a shared_ptr is known for this Ref */
bool resolved () const {
return static_cast<bool>(_object);
}
private:
std::string _id; ///< ID; will always be known
boost::shared_ptr<T> _object; ///< shared_ptr to the thing, may be null.
};
}
#endif
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