C++ Boost状态机语言--`action中的`post`事件`

我已经使用了几天，现在我需要在一个动作中发布/处理一个事件。 我可以从转换表中直接看到：

使用名称空间sml； 返回make_transition_表 *s1_s+事件/过程_事件其他_事件{}=s2_s， s2_s+事件=X ; 但我的用例不同： 我有一个状态，它有一个actionfor on entry事件，它执行一些工作，并最终从状态操作中触发一个事件

例如，使用boost statechart，每个状态都可以访问上下文并可以发布事件

---

这在sml中是可能的吗？

这是可能的。你需要做两件事。 一种是将boost:：sml:：queue模板参数设置为boost:：sml:：sm

参数进程是可调用的。所以您可以将进程作为函数调用。调用processevent时，事件将被发布到队列中

下面是一个示例代码：

#include <iostream>
#include <queue>
#include <boost/sml.hpp>

int main() {
    namespace sml = boost::sml;

    struct my_event {};
    struct other_event {};

    struct table {
        auto operator()() const noexcept {
            using namespace sml;
            return make_transition_table(

               *"s1"_s + event<my_event> / 
                // In order to post event in the action,
                // you need to define the action handler as follows.
                // The key is the second parameter.
                // `sml::back::process` is posting event callable type.
                // You need to pass all event types that are posted in the action handler
                // as the template argument.
                // Unfortunately you cannot write `sml::back::process<_>` for all events.
                [](auto const& /*ev*/, sml::back::process<other_event /*, my_event*/ > process) {
                    std::cout << "before post" << std::endl;
                    process(other_event{});
                    std::cout << "after post" << std::endl;
                } = "s2"_s,

                "s2"_s + event<other_event> = X,

                // entry exit log
                "s1"_s + sml::on_entry<_> / [] { std::cout << "s1 on entry" << std::endl; },
                "s1"_s + sml::on_exit<_>  / [] { std::cout << "s1 on exit"  << std::endl; },
                "s2"_s + sml::on_entry<_> / [] { std::cout << "s2 on entry" << std::endl; },
                "s2"_s + sml::on_exit<_>  / [] { std::cout << "s2 on exit"  << std::endl; }
            );
        };
    };

    // sml::process_queue is for post event
    sml::sm<table, sml::process_queue<std::queue>> sm;
    sm.process_event(my_event{});
}

---

现场演示：

这是可能的。你需要做两件事。 一种是将boost:：sml:：queue模板参数设置为boost:：sml:：sm

参数进程是可调用的。所以您可以将进程作为函数调用。调用processevent时，事件将被发布到队列中

下面是一个示例代码：

#include <iostream>
#include <queue>
#include <boost/sml.hpp>

int main() {
    namespace sml = boost::sml;

    struct my_event {};
    struct other_event {};

    struct table {
        auto operator()() const noexcept {
            using namespace sml;
            return make_transition_table(

               *"s1"_s + event<my_event> / 
                // In order to post event in the action,
                // you need to define the action handler as follows.
                // The key is the second parameter.
                // `sml::back::process` is posting event callable type.
                // You need to pass all event types that are posted in the action handler
                // as the template argument.
                // Unfortunately you cannot write `sml::back::process<_>` for all events.
                [](auto const& /*ev*/, sml::back::process<other_event /*, my_event*/ > process) {
                    std::cout << "before post" << std::endl;
                    process(other_event{});
                    std::cout << "after post" << std::endl;
                } = "s2"_s,

                "s2"_s + event<other_event> = X,

                // entry exit log
                "s1"_s + sml::on_entry<_> / [] { std::cout << "s1 on entry" << std::endl; },
                "s1"_s + sml::on_exit<_>  / [] { std::cout << "s1 on exit"  << std::endl; },
                "s2"_s + sml::on_entry<_> / [] { std::cout << "s2 on entry" << std::endl; },
                "s2"_s + sml::on_exit<_>  / [] { std::cout << "s2 on exit"  << std::endl; }
            );
        };
    };

    // sml::process_queue is for post event
    sml::sm<table, sml::process_queue<std::queue>> sm;
    sm.process_event(my_event{});
}

现场演示：

#include <iostream>
#include <queue>
#include <boost/sml.hpp>

int main() {
    namespace sml = boost::sml;

    struct my_event {};
    struct other_event {};

    struct table {
        auto operator()() const noexcept {
            using namespace sml;
            return make_transition_table(

               *"s1"_s + event<my_event> / 
                // In order to post event in the action,
                // you need to define the action handler as follows.
                // The key is the second parameter.
                // `sml::back::process` is posting event callable type.
                // You need to pass all event types that are posted in the action handler
                // as the template argument.
                // Unfortunately you cannot write `sml::back::process<_>` for all events.
                [](auto const& /*ev*/, sml::back::process<other_event /*, my_event*/ > process) {
                    std::cout << "before post" << std::endl;
                    process(other_event{});
                    std::cout << "after post" << std::endl;
                } = "s2"_s,

                "s2"_s + event<other_event> = X,

                // entry exit log
                "s1"_s + sml::on_entry<_> / [] { std::cout << "s1 on entry" << std::endl; },
                "s1"_s + sml::on_exit<_>  / [] { std::cout << "s1 on exit"  << std::endl; },
                "s2"_s + sml::on_entry<_> / [] { std::cout << "s2 on entry" << std::endl; },
                "s2"_s + sml::on_exit<_>  / [] { std::cout << "s2 on exit"  << std::endl; }
            );
        };
    };

    // sml::process_queue is for post event
    sml::sm<table, sml::process_queue<std::queue>> sm;
    sm.process_event(my_event{});
}