EM-Promise

A promise / deferred implementation for EventMachine inspired by AngularJS / Kris Kowal’s Q.

From the perspective of dealing with error handling, deferred and promise apis are to asynchronous programing what try, catch and throw keywords are to synchronous programming.

require 'rubygems'
require 'em-promise'

def asyncGreet(name)
  deferred = EM::Q.defer
  
  EM::Timer.new(5) do
    EM.defer do
      deferred.resolve("Hello #{name}")
    end
  end
  
  deferred.promise
end


EventMachine.run do

  asyncGreet('Robin Hood').then(proc { |greeting|
    p "Success: #{greeting}"
  }, proc { |reason|
    p "Failed: #{reason}"
  })
  
  asyncGreet('The Dude').then do |greeting|
    p "Jeff '#{greeting}' Lebowski"
  end
  
end

Start using it now

1. Read the Documentation
2. Then gem install em-promise