libs/local_function/example/scope_exit.cpp
// Copyright (C) 2009-2012 Lorenzo Caminiti
// Distributed under the Boost Software License, Version 1.0
// (see accompanying file LICENSE_1_0.txt or a copy at
// http://www.boost.org/LICENSE_1_0.txt)
// Home at http://www.boost.org/libs/local_function
#include "scope_exit.hpp"
#include <boost/foreach.hpp>
#include <boost/typeof/typeof.hpp>
#include <boost/typeof/std/vector.hpp>
#include BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP()
#include <boost/detail/lightweight_test.hpp>
#include <vector>
#include <iostream>
#include <sstream>
class person {
friend class world;
public:
typedef unsigned int id_t;
typedef unsigned int evolution_t;
person(void): id_(0), evolution_(0) {}
friend std::ostream& operator<<(std::ostream& o, person const& p) {
return o << "person(" << p.id_ << ", " << p.evolution_ << ")";
}
private:
id_t id_;
evolution_t evolution_;
};
BOOST_TYPEOF_REGISTER_TYPE(person)
class world {
public:
typedef unsigned int id_t;
world(void): next_id_(1) {}
void add_person(person const& a_person);
friend std::ostream& operator<<(std::ostream& o, world const& w) {
o << "world(" << w.next_id_ << ", {";
BOOST_FOREACH(person const& p, w.persons_) {
o << " " << p << ", ";
}
return o << "})";
}
private:
id_t next_id_;
std::vector<person> persons_;
};
BOOST_TYPEOF_REGISTER_TYPE(world)
void world::add_person(person const& a_person) {
persons_.push_back(a_person);
// This block must be no-throw.
//[scope_exit
person& p = persons_.back();
person::evolution_t checkpoint = p.evolution_;
SCOPE_EXIT(const bind checkpoint, const bind& p, bind this_) {
if (checkpoint == p.evolution_) this_->persons_.pop_back();
} SCOPE_EXIT_END
//]
// ...
checkpoint = ++p.evolution_;
// Assign new id to the person.
world::id_t const prev_id = p.id_;
p.id_ = next_id_++;
SCOPE_EXIT(const bind checkpoint, const bind prev_id, bind& p,
bind& next_id_) {
if (checkpoint == p.evolution_) {
next_id_ = p.id_;
p.id_ = prev_id;
}
} SCOPE_EXIT_END
// ...
checkpoint = ++p.evolution_;
}
int main(void) {
person adam, eva;
std::ostringstream oss;
oss << adam;
std::cout << oss.str() << std::endl;
BOOST_TEST(oss.str() == "person(0, 0)");
oss.str("");
oss << eva;
std::cout << oss.str() << std::endl;
BOOST_TEST(oss.str() == "person(0, 0)");
world w;
w.add_person(adam);
w.add_person(eva);
oss.str("");
oss << w;
std::cout << oss.str() << std::endl;
BOOST_TEST(oss.str() == "world(3, { person(1, 2), person(2, 2), })");
return boost::report_errors();
}