Shouter is a very simple and lightweight publish/subscription DSL for Ruby applications.

Add this line to your application's Gemfile:

gem 'shouter'

And then execute:

$ bundle

Or install it yourself as:

$ gem install shouter

class A
  extend Shouter
  subscribe(Listener.new, for: :my_scope)
end

class Listener
  def on_change
    "I`m changed"
  end
end

A.publish(:my_scope, :on_change)
=> "I`m changed"

Since version 0.1.3 if you want asyncronous execution, using separate threads you can supply the async option. By default it is set to false

class A
  extend Shouter
  subscribe(Listener.new, for: :my_async_scope, async: true)
end

Now whenever you publish and event it will be run in a separate thread. If a thread for the execution is already present another one will not be created. If you have supplied a callback option it will be executed in the thread of execution of the listener.

You can subscribe multiple objects:

class A
  extend Shouter
  subscribe(Listener.new, Listener1.new, Listener2.new, for: :my_scope)
end

You can subscribe an object for single execution, after that the object will be removed from the listener store

class A
  extend Shouter
  subscribe(Listener.new, for: :my_scope, single: true)
end

A.publish(:my_scope, :on_change)
=> "I`m changed"

A.publish(:my_scope, :on_change)
=> nil

All the arguments are passed to the method as well:

A.publish(:my_scope, :on_change_with_arguments, 'argument_1', 'argument_2')

You can also pass a block to the publish method, which will serve as a successful callback, meaning it will only get executed after the event has been triggered

A.publish(:my_scope, :on_change) do
  puts "I am callback"
end

To unsubscribe single or multiple objects you can call the unsubscribe method

A.unsubscribe(Listener1, Listener2)

Since version 1.0.1:

Alternatively you can pass the callback option when subscribing. It accepts a callable object:

subscribe(Listener.new, for: :my_scope, callback: ->() { perform_async })

You can now add a guard clause which will stop the execution of events unless it returns true. Guard clauses accept callable objects

subscribe(Listener.new, for: :my_scope, guard: Proc.new { some_listener.respond_to?(:my_method) })

The clear method removes all listeners from the store.

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/wizardone/shouter. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.