2 Copyright (C) 2014 Carl Hetherington <cth@carlh.net>
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
27 #include "exceptions.h"
30 #include <boost/shared_ptr.hpp>
36 * @brief A reference to an object which is identified by a universally-unique identifier (UUID).
38 * This class is a `pointer' to a thing. It will always know the
39 * UUID of the thing, and it may have a shared_ptr to the C++ object
40 * which represents the thing.
42 * If the Ref does not have a shared_ptr it may be given one by
43 * calling resolve() with a list of objects. The shared_ptr will be
44 * set up using any object on the list which has a matching ID.
50 /** Initialise a Ref with an ID but no shared_ptr */
55 /** Initialise a Ref with a shared_ptr to an object */
56 Ref (boost::shared_ptr<T> object)
61 /** Set the ID of this Ref */
62 void set_id (std::string id)
67 /** Look through a list of objects and copy a shared_ptr to any object
68 * which matches the ID of this one.
70 void resolve (std::list<boost::shared_ptr<Object> > objects)
72 typename std::list<boost::shared_ptr<Object> >::iterator i = objects.begin();
73 while (i != objects.end() && !ids_equal ((*i)->id(), _id)) {
77 if (i != objects.end ()) {
78 _object = boost::dynamic_pointer_cast<T> (*i);
82 /** @return the ID of the thing that we are pointing to */
83 std::string id () const {
87 /** @return a shared_ptr to the thing; an UnresolvedRefError is thrown
88 * if the shared_ptr is not known.
90 boost::shared_ptr<T> object () const {
92 throw UnresolvedRefError (_id);
98 /** operator-> to access the shared_ptr; an UnresolvedRefError is thrown
99 * if the shared_ptr is not known.
101 T * operator->() const {
103 throw UnresolvedRefError (_id);
106 return _object.get ();
109 /** @return true if a shared_ptr is known for this Ref */
110 bool resolved () const {
115 std::string _id; ///< ID; will always be known
116 boost::shared_ptr<T> _object; ///< shared_ptr to the thing, may be null.