EventBus

Simple and very fast event bus. The EventBus library is a convenient realization of the observer pattern. It works perfectly to supplement the implementation of MVC logic (model-view-controller) in event-driven UIs

General concept

EventBus was created because I want something easy to use and faster than CCNotificationCenter from cocos2d-x library. Of course C++11 support was mandatory at that moment.

EventBus main goals:

Fast
Easy to use
Strongly typed
Free
tiny (~37 KB)
Decouples notification senders and receivers
on every platform you need (cross-platform)

Brief @ presentation

Presentation google docs

Sample / use cases

You can checkout use_case/
If you want to play with sample online checkout this link: wandbox.org

Usage

Store bus

// store it in controller / singleton / std::shared_ptr whatever you want
auto bus = std::make_shared<EventBus>();

Define events

namespace event // optional namespace
{
	struct Gold
	{
		int goldReceived = 0;
	};

	struct OK {}; // Simple event when user press "OK" button
}

// ...
dexode::EventBus::Listener listener{bus};
listener.listen([](const event::Gold& event) // listen with lambda
                {
                     std::cout << "I received gold: " << event.goldReceived << " 💰" << std::endl;
                });

HudLayer* hudLayer;
// Hud layer will receive info about gold
hudLayer->listener.listen<event::Gold>(std::bind(&HudLayer::onGoldReceived, hudLayer, std::placeholders::_1));

Spread the news

//Inform listeners about event
bus->postpone(event::Gold{12}); // 1 way
bus->postpone<event::Gold>({12}); // 2 way

event::Gold myGold{12};
bus->postpone(myGold); // 3 way

Process the events

bus->process();

Checkout tests or use cases for more examples. Or create issue what isn't clear :)

Add to your project

EventBus can be added as ADD_SUBDIRECTORY to your cmake file. Then simply link it via TARGET_LINK_LIBRARIES Example:

# No tests/benchmarks target won't be added. Root CMakeLists is for development.
ADD_SUBDIRECTORY(path/to/EventBus/lib)
ADD_EXECUTABLE(MyExecutable
		main.cpp
		)

TARGET_LINK_LIBRARIES(MyExecutable PUBLIC Dexode::EventBus)

Also if you want you can install library and add it at any way you want. Eg.

mkdir -p lib/build/
cd lib/build
cmake -DCMAKE_BUILD_TYPE=Relase -DCMAKE_INSTALL_PREFIX=~/.local/ ..

cmake --build . --target install
# OR
make && make install

Now in Release/install library is placed.

Or, you can install the library through your package manager (dpkg, rpm, etc). E.g.

mkdir -p lib/build/
cd lib/build

# For most RH-based Distributions
cmake -DCMAKE_BUILD_TYPE=Relase -DCPACK_GENERATOR="RPM" ..

# For most Debian-based Distributions
cmake -DCMAKE_BUILD_TYPE=Relase -DCPACK_GENERATOR="DEB" ..

# Or for both of them
cmake -DCMAKE_BUILD_TYPE=Relase -DCPACK_GENERATOR="RPM;DEB" ..

cmake --build . --target package
# Or
make package

# For most Debian-based systems
sudo dpkg -i EventBus*.deb

# For most RH-based systems
sudo rpm -i EventBus*.rpm
# OR
sudo yum install EventBus*.rpm

Performance (could be outdated)

I have prepared some performance results. You can read about them here Small example:

check10NotificationsFor1kListeners                                     263 ns        263 ns    2668786 sum=-1.76281G
check10NotificationsFor1kListeners_CCNotificationCenter              11172 ns      11171 ns      62865 sum=54.023M

checkNotifyFor10kListenersWhenNoOneListens                              18 ns         18 ns   38976599 sum=0
checkNotifyFor10kListenersWhenNoOneListens_CCNotificationCenter     127388 ns     127378 ns       5460 sum=0