eventpp -- C++ library for event dispatcher and callback list

eventpp is a C++ library that provides tools that allow your application components to communicate with each other by dispatching events and listening to them. With eventpp you can implement signal/slot mechanism, or observer pattern, very easily.

Facts and features

Supports both synchronous event dispatching (EventDispatcher) and asynchronous event queue (EventQueue).
Supports nested event. A listener can safely dispatch event, append/prepend/insert/remove other listeners, during capturing an event.
Configurable and extensible with policies and mixins.
Supports event filter via mixins.
Supports multiple threading.
Template based, less runtime overhead, unlimited possibilities. The event and callback can be almost any C++ types that satisfy minimum requirements.
Backed by unit tests.
Written in portable and standard C++. (I'm not a C++ standard expert so if you find any non-standard code or undefined behavior please let me know.)
Requires C++ 11 (tested with MSVC 2017, MSVC 2015, MinGW (Msys) gcc 7.2, and Ubuntu gcc 5.4).
Doesn't depend on any other libraries.
Header only, no source file, no need to build.

License

Apache License, Version 2.0

Version 0.1.0

eventpp is currently usable and near stable.

Source code

https://github.com/wqking/eventpp

Quick start

Namespace

eventpp

Using CallbackList

#include "eventpp/callbacklist.h"
eventpp::CallbackList<void (const std::string &, const bool)> callbackList;
callbackList.append([](const std::string & s, const bool b) {
	std::cout << std::boolalpha << "Got callback 1, s is " << s << " b is " << b << std::endl;
});
callbackList.append([](std::string s, int b) {
	std::cout << std::boolalpha << "Got callback 2, s is " << s << " b is " << b << std::endl;
});
callbackList("Hello world", true);

Using EventDispatcher

#include "eventpp/eventdispatcher.h"
eventpp::EventDispatcher<int, void ()> dispatcher;
dispatcher.appendListener(3, []() {
	std::cout << "Got event 3." << std::endl;
});
dispatcher.appendListener(5, []() {
	std::cout << "Got event 5." << std::endl;
});
dispatcher.appendListener(5, []() {
	std::cout << "Got another event 5." << std::endl;
});
// dispatch event 3
dispatcher.dispatch(3);
// dispatch event 5
dispatcher.dispatch(5);

Using EventQueue

eventpp::EventQueue<int, void (const std::string &, const bool)> queue;

dispatcher.appendListener(3, [](const std::string s, bool b) {
	std::cout << std::boolalpha << "Got event 3, s is " << s << " b is " << b << std::endl;
});
dispatcher.appendListener(5, [](const std::string s, bool b) {
	std::cout << std::boolalpha << "Got event 5, s is " << s << " b is " << b << std::endl;
});

// The listeners are not triggered during enqueue.
queue.enqueue(3, "Hello", true);
queue.enqueue(5, "World", false);

// Process the event queue, dispatch all queued events.
queue.process();

Documentations

Build the unit tests

The library itself is header only and doesn't need building.
The unit test requires CMake to build, and there is a makefile to ease the building.
Go to folder tests/build, then run make with different target.

make vc17 #generate solution files for Microsoft Visual Studio 2017, then open eventpptest.sln in folder project_vc17
make vc15 #generate solution files for Microsoft Visual Studio 2015, then open eventpptest.sln in folder project_vc15
make mingw #build using MinGW
make linux #build on Linux

Motivations

I (wqking) am a big fan of observer pattern (publish/subscribe pattern), I used such pattern a lot in my code. I either used GCallbackList in my cpgf library which is too simple and not safe (not support multi threading nor nested event), or repeated coding event dispatching mechanism such as I did in my Gincu game engine (the latest version has be rewritten to use eventpp). Both approaches are neither fun nor robust.
Thanking to C++11, now it's quite easy to write a reusable event library with beautiful syntax (it's a nightmare to simulate the variadic template in C++03), so here comes eventpp.

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