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

0. Store bus

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

1. Define events

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

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

2. Subscribe

// ...
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));

3. 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

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

Issues ?

Please report here issue / question / whatever, there is chance 99% I will answer ;)

If you have any questions or want to chat use gitter.

Tesing and metrics

// TODO

Thanks to

• staakk for fixing windows ;) 53d5026
• kuhar for his advice and suggestions for EventBus
• swietlana for English correction and support ;)
• ruslo for this great example: https://github.com/forexample/package-example

For modern cmake refer

• https://github.com/forexample/package-example
• https://www.youtube.com/watch?v=6sWec7b0JIc

License

EventBus source code can be used according to the Apache License, Version 2.0. For more information see LICENSE file

If you don't like to read to much here is sumup about license Apache 2.0