RubyMotion async module that gives a pretty syntax.

app_delegate.rb

class AppDelegate
  include Async

  def application(application, didFinishLaunchingWithOptions:launchOptions)

    thread_1 = async do
      i = 0
      300_000.times do
        sleep 0.000001
        i += (300_000 - i)
      end
      main { puts i }
    end

    thread_2 = async do
      i = 0
      900_000.times do
        sleep 0.000001
        i += (900_000 - i)
      end
      main { puts i }
    end

    after thread_1, thread_2 do
      puts "They're both done."
    end

    true
  end
end

rm-async.rb

module Async
  def async(&callback)
    GroupAsync.new.async(&callback)
  end

  def main(&callback)
    Dispatch::Queue.main.async(&callback)
  end

  def after(*asyncs, &callback)
    async do
      asyncs.each{|a| a.group.wait }
      callback.call
    end
  end

  class GroupAsync
    attr_reader :group

    def initialize
      @group = Dispatch::Group.new
    end

    def async(&callback)
      Dispatch::Queue.concurrent.async(group) do
        callback.call
      end
      self
    end
    alias_method :and, :async

    def then(&callback)
      Dispatch::Queue.concurrent.async do
        group.wait
        callback.call
      end
      self
    end
  end
end