Evented

A micro library providing Crystal objects with Publish-Subscribe capabilities

• Decouple core business logic from external concerns in Hexagonal style architectures
• Use as an alternative to callbacks and Observers
• Connect objects based on context without permanence
• React to events synchronously

Installation

Add this to your application's shard.yml:

dependencies:
  evented:
    github: krisleech/evented

Usage

Publishing

By including Evented::Publisher your objects get broadcast and subscribe methods.

broadcast can be called from within your object whenever you want to broadcast a significant event.

require "evented"

class MyPublisher
  include Evented::Publisher

  def call(input)
    result = do_something(input)
    broadcast(:something_happened, result)
  end
end

Subscribing

To subscribe an object to receive events include Evented::Subscriber and provide your own on_event method which will receive 2 arguments, the event_name and payload.

require "evented"

class MySubscriber
  include Evented::Subscriber

  def on_event(event_name, payload)
    # ...
  end
end

To subscribe the listener to a publisher:

publisher = MyPublisher.new
publisher.subscribe(MySubscriber.new)

publisher.call("hello")

In the above example the subscriber will have on_event(:something_happened, "hello") called.

Development

Specs

crystal spec

Automatically run Specs

ls ./**/*.cr | entr crystal spec

Contributing

1. Fork it ( https://github.com/krisleech/evented/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• Kris Leech - creator, maintainer