如何重置提升::sml::sm 实例

How to reset boost::sml::sm instance

本文关键字：sml 实例 sm 何重置      更新时间：2023-10-16

似乎boost::sml::sm没有任何特定的重置方法，并且缺少移动分配运算符，因此我无法执行诸如分配新实例之类的操作(例如machine = boost::sml::sm<MyMachine>{}(。我目前的方法是一个丑陋的技巧，将 dtor 和 ctor 调用到位：

machine.~sm();
new (&machine) std::decay_t<decltype(machine)>();

有没有更好的方法？

就像你往常做的那样(即从不做你实际写的东西(：使用包装器来管理生命周期，例如使用optional或unique_ptr.

例：

住在科里鲁 

//
// Copyright (c) 2016-2018 Kris Jusiak (kris at jusiak dot net)
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
#include <boost/sml.hpp>
#include <cassert>
namespace sml = boost::sml;
namespace {
// events
struct release {};
struct ack {};
struct fin {};
struct timeout {};
// guards
const auto is_ack_valid = [](const ack&) { return true; };
const auto is_fin_valid = [](const fin&) { return true; };
// actions
const auto send_fin = [] {};
const auto send_ack = [] {};
struct hello_world {
auto operator()() const {
using namespace sml;
// clang-format off
return make_transition_table(
*"established"_s + event<release> / send_fin = "fin wait 1"_s,
"fin wait 1"_s + event<ack> [ is_ack_valid ] = "fin wait 2"_s,
"fin wait 2"_s + event<fin> [ is_fin_valid ] / send_ack = "timed wait"_s,
"timed wait"_s + event<timeout> / send_ack = X
);
// clang-format on
}
};
}
#include <boost/optional.hpp>
#include <iostream>
int main() {
using namespace sml;
boost::optional<sm<hello_world> > m;
static_assert(2 == sizeof(m), "sizeof(m) != 2b");
auto run = [&] {
assert(m->is("established"_s));
m->process_event(release{});
assert(m->is("fin wait 1"_s));
m->process_event(ack{});
assert(m->is("fin wait 2"_s));
m->process_event(fin{});
assert(m->is("timed wait"_s));
m->process_event(timeout{});
assert(m->is(X));  // released
};
for (auto i : {1,2,3}) {
std::cout << "Run " << i << "n";
m.emplace(); // default constructs a sm in-place
run();
}
}

指纹

Run 1
Run 2
Run 3
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