Events

Super basic event emitter written for crystal-lang.

Installation

Add this to your application's shard.yml:

dependencies:
  events:
    github: kcreate/events
    branch: master

Example

Just include the module inside any classes you want to have access to the event methods

require "events"

# Some class
class Person
  include Events

  def initialize
    add_event "fart"
  end

  def fart
    invoke_event "fart"
  end
end

leonard = Person.new
leonard.on "fart", do
  puts "daaamn"
end
leonard.fart

You should see "daaamn" pop up in your console

Usage

The test suite has all the examples you need. I usually forget to update the README so just look there.

You first need a class that will emit some events. Add the module to your class like this:

class Person
  include Events
end

You should add all your events inside your initialize function to prevent unexpected behaviour. Use add_event for this.

class Person
  include Events

  def initialize
    add_event "wakeup"
    add_event "sleep"
  end

  def wakeup
    invoke_event "wakeup"
  end

  def gotosleep
    invoke_event "sleep"
  end

  # ... The rest of your class
end

Similarly you can remove an event using remove_event. I don't know why you'd want to remove an event, but you can.

class Person
  include Events

  def initialize
    add_event "wakeup"
    add_event "sleep"
  end

  def wakeup
    invoke_event "wakeup"
  end

  def gotosleep

    # This first invokes the event and deletes it afterwards

    invoke_event "sleep"
    remove_event "sleep"
  end
end

You can subscribe to these events from the outside like this:

class Person
  ...
end

leonard = Person.new

leonard.on "wakeup" do
  puts "leonard woke up"
end

leonard.on "sleep" do
  puts "leonard went to sleep"
end

If you now call the wakeup and gotosleep functions,

leonard.gotosleep
leonard.wakeup

This will be the output in your console

leonard went to sleep
leonard woke up

Calling the on function will add your handler to the event, but also return a proc that removes the handler from the event again. This means you can do stuff like this:

sleephandler = leonard.on "sleep" do
    puts "going to sleep"
end

leonard.gotosleep # going to sleep
leonard.gotosleep # going to sleep

sleephandler.call # removing the handler

leonard.gotosleep # ... nothing will be printed

Test

Run crystal spec to run the test suite.

Todos

• Allow passing arguments to callbacks
• Allow the usage of subclasses of Event
• Add docs to a public website

Contributing

1. Fork it ( https://github.com/kcreate/events/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Make sure your changes don't break anything (crystal spec)
5. Push to the branch (git push origin my-new-feature)
6. Create a new Pull Request

Contributors

• kcreate Leonard Schuetz - creator, maintainer