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