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// Copyright Louis Dionne 2013-2017
// Distributed under the Boost Software License, Version 1.0.
#include <boost/hana/assert.hpp>
#include <boost/hana/at_key.hpp>
#include <boost/hana/contains.hpp>
#include <boost/hana/map.hpp>
#include <boost/hana/pair.hpp>
#include <boost/hana/string.hpp>
#include <functional>
#include <string>
#include <vector>
namespace hana = boost::hana;
template <typename ...Events>
struct event_system {
using Callback = std::function<void()>;
hana::map<hana::pair<Events, std::vector<Callback>>...> map_;
template <typename Event, typename F>
void on(Event e, F handler) {
auto is_known_event = hana::contains(map_, e);
static_assert(is_known_event,
"trying to add a handler to an unknown event");
map_[e].push_back(handler);
}
template <typename Event>
void trigger(Event e) const {
auto is_known_event = hana::contains(map_, e);
static_assert(is_known_event,
"trying to trigger an unknown event");
for (auto& handler : this->map_[e])
handler();
}
};
template <typename ...Events>
event_system<Events...> make_event_system(Events ...events) {
return {};
}
int main() {
auto events = make_event_system(
BOOST_HANA_STRING("foo"),
BOOST_HANA_STRING("bar"),
BOOST_HANA_STRING("baz")
);
std::vector<std::string> triggered_events;
events.on(BOOST_HANA_STRING("foo"), [&] {
triggered_events.push_back("foo:1");
});
events.on(BOOST_HANA_STRING("foo"), [&] {
triggered_events.push_back("foo:2");
});
events.on(BOOST_HANA_STRING("bar"), [&] {
triggered_events.push_back("bar:1");
});
events.on(BOOST_HANA_STRING("baz"), [&] {
triggered_events.push_back("baz:1");
});
events.trigger(BOOST_HANA_STRING("foo"));
events.trigger(BOOST_HANA_STRING("bar"));
events.trigger(BOOST_HANA_STRING("baz"));
BOOST_HANA_RUNTIME_CHECK(triggered_events == std::vector<std::string>{
"foo:1", "foo:2", "bar:1", "baz:1"
});
}
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