A Pure-Ruby dispatcher for writing eventful programs. This does not depend on any external event source, so there is no need for a C interface. Events and handlers can be any Ruby object.

• Prerequisite: Ruby 1.9. This library rely’s om Fibers. Should work with the backported Fiber library for 1.8

sudo gem install event-engine

require "pathname"
require "event-engine"

eng = EventEngine::Engine.new

eng.setup do |en|
  en.on_file {|ev| puts "file: " + ev.to_s}
  en.on_directory {|ev| puts "dir: " + ev.to_s}
end

# walk tree triggering events for each node
Dir['../**/*'].each {|l| eng.trigger Pathname.new(l)}

produces recursive listing of directory tree

Setting up a handler can take either a Proc or a Module with at least 2 methods defined, interested?(ev) and handle(ev). Or it can take a “on_xxxx” method which combines the filter and is passed a bloxk that handles the event.

If a module, then the handle method must return the event, possibly modifying it first. Bare procs and “on_xxxx” handlers automatically return the event so there is no need to do it in the proc/block.

Events are chained from one handler to the next. The order of execution is FIFO.

Modules must state their interest in an event with interested?(ev). Or they can include AlwaysInterested to see all events.

Procs are (currently) defined as being interested in all events.

on_xxxx style events are subscribed to events that match the suffix of “on_xxxx”. These look fir matching events based on either the name or a matching predicate. E.g.:

class Event
  def name; "cool"; end
end

eng.on_cool {|ev| puts in cool}

Or for predicates:

# class Pathname.directory? and .file?

eng.on_dir {|ev| puts "dir: #{ev.to_s}"}
eng.on_file {|ev| puts "file: #{ev.to_s}"}

Or make your own event type. It should have either a name method/attribute or a predicate.

• Fork the project.

• Make your feature addition or bug fix.

• Add tests for it. This is important so I don’t break it in a future version unintentionally.

• Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)

• Send me a pull request. Bonus points for topic branches.

Copyright © 2010 Ed Howland. See LICENSE for details.