Module: Tusk::Observable::DRb

Defined in:
lib/tusk/observable/drb.rb

Overview

An observer implementation for DRb. This module requires that you start a DRb server, which can be done via Server.start

This observer works across processes.

Example:

require 'tusk/observable/drb'

class Timer
  include Tusk::Observable::DRb

  # Start the DRb server. Do this once
  Thread.new { Server.start }

  def tick
    changed
    notify_observers
  end
end

class Listener
  def update
    puts "got update"
  end
end

timer = Timer.new

fork do
  timer.add_observer Listener.new
  sleep # put the process to sleep so it doesn't exit
end

loop do
  timer.tick
  sleep 1
end

Defined Under Namespace

Classes: Proxy, Server

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.extended(klass) ⇒ Object 



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# File 'lib/tusk/observable/drb.rb', line 93

def self.extended klass
  super

  klass.instance_eval do
    @bus = DRbObject.new_with_uri uri
    @observer_state = false
    @subscribers      = {}
  end
end

Instance Method Details

#add_observer(object, func = :update) ⇒ Object

Add observer as an observer to this object. The object will receive a notification when #changed? returns true and #notify_observers is called.

func method is called on object when notifications are sent.



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# File 'lib/tusk/observable/drb.rb', line 116

def add_observer object, func = :update
  unless ::DRb.thread && ::DRb.thread.alive?
    ::DRb.start_service
  end

  proxy = Proxy.new object, func
  @subscribers[object] = proxy
  @bus.watch channel, proxy
end

#changed(state = true) ⇒ Object

Set the changed state of this object. Notifications will be sent only if the changed state is a truthy object.



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# File 'lib/tusk/observable/drb.rb', line 156

def changed state = true
  @observer_state = state
end

#changed? ⇒ Boolean

Returns true if this object's state has been changed since the last call to #notify_observers.

Returns:

  • (Boolean) 


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# File 'lib/tusk/observable/drb.rb', line 150

def changed?
  @observer_state
end

#count_observers ⇒ Object

Returns the number of observers associated with this object in the current process. If the object is observed across multiple processes, the returned count will not reflect the other processes.



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# File 'lib/tusk/observable/drb.rb', line 163

def count_observers
  @subscribers.length
end

#delete_observer(o) ⇒ Object

Remove observer so that it will no longer receive notifications.



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# File 'lib/tusk/observable/drb.rb', line 143

def delete_observer o
  proxy = @subscribers.delete o
  @bus.delete_observer channel, proxy
end

#delete_observers ⇒ Object

Remove all observers associated with this object in the current process. This method will not impact observers of this object in other processes.



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# File 'lib/tusk/observable/drb.rb', line 137

def delete_observers
  @bus.delete channel
  @subscribers.clear
end

#initialize(*args) ⇒ Object 



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# File 'lib/tusk/observable/drb.rb', line 103

def initialize *args
  super

  @bus = DRbObject.new_with_uri uri
  @observer_state = false
  @subscribers      = {}
end

#notify_observers(*args) ⇒ Object

If this object's #changed? state is true, this method will notify observing objects.



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# File 'lib/tusk/observable/drb.rb', line 128

def notify_observers(*args)
  return unless changed?
  @bus.signal channel, args
  changed false
end