boost::signals2 c++, c++ signal/slot pattern.

Namespace

namespace alias

namespace sig = boost::signals2;

Signal Type

The signal type of boost::signals2

using signal_type = sig::signal<return_type(param_type)>;

Slot Type

The slot type of boost::signals2

using slot_type = signal_type::slot_type;

Connection Type

The connection type of signal/slot.

using connection_type = boost::signals2::connection;

c++ example

#include <boost/signals2.hpp>
#include <iostream>
#include <functional>

namespace sig = boost::signals2;

namespace nsd
{
	using signal_type = sig::signal<int(int)>;
	using slot_type = nsd::signal_type::slot_type;
	using connection_type = sig::connection;
	using std::placeholders::_1;
	using std::placeholders::_2;
	using std::placeholders::_3;
}

namespace nsd
{
	class event
	{
	private:
		nsd::signal_type __signal;
	public:
		nsd::connection_type connect(int prior__, const nsd::slot_type & slot__)
		{
			return __signal.connect(prior__, slot__);
		}
		void update(int value)
		{
			auto result = __signal(value);
			if (result)
				std::cout << "result: " << *result << std::endl;
			else
				std::cout << "no result" << std::endl;
		}
	};

	class viewer
	{
	private:
		int __prior;
		nsd::connection_type __connection;
	public:
		viewer(int prior__, nsd::event & event__):
			__prior{prior__},
			__connection{
				event__.connect(
					__prior,
					std::bind(
						&nsd::viewer::upgrade,
						this,
						_1
					)
				)
			}
		{
		}
	public:
		virtual ~viewer()
		{
			__connection.disconnect();
		}
	public:
		int upgrade(int value__)
		{
			int x = value__ * value__ * value__;
			std::cout << __prior << " : " << x << std::endl;
			return x;
		}
	};
}

int main()
{
	nsd::event event;
	nsd::viewer v1{10, event};
	nsd::viewer v2{20, event};
	event.update(5);
	event.update(7);
}

Date

Sat Jun 7 06:34:55 AM UTC 2025

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