CODEWITHSUNDEEP
ruby-on-rails-3
stackOverlord
stackOverlord

Reputation: 5412

How do I create a singleton global object in rails?

I have an object that I want created once and accessible in one of my models. Where do I put him? I'm afraid if I put him in the model class file he'll get created every time I make a new instance of that model. I only want this object created once at start up. Here's the object:

require 'pubnub'    
publish_key   = 'fdasfs'
subscribe_key = 'sdfsdsf'
secret_key    = 'fsdfsd'
ssl_on        = false

pubnub_obj = Pubnub.new(publish_key,
                    subscribe_key,
                    secret_key,
                    ssl_on)

I use him like this in the model:

class Message < ActiveRecord::Base

  def self.send_new_message_client(message)
    message = { 'some_data' => message }
    info = pubnub_obj.publish({
                            'channel' => 'testing',
                            'message' => message
                          })
    puts(info)
  end

end

Upvotes: 30

Views: 27615

Answers (2)

iHiD
iHiD

Reputation: 2438

If you want only one instance in your whole application, use a singleton, otherwise use a class variable.

To use a singleton, include the Singleton mixin.

require 'singleton'

class Pubnub
  include Singleton

  attr_writer :publish_key, :subscribe_key, :secret_key, :ssl_on

  def publish
    #...
  end
end

and then use it like this:

require 'pubnub'    
class Message < ActiveRecord::Base
  Pubnub.instance.publish_key = 'xyz'
  Pubnub.instance.subscribe_key = 'xyz'
  Pubnub.instance.secret_key = 'xyz'
  Pubnub.instance.ssl_on = 'xyz'

  def self.send_new_message_client(message)
    message = { 'some_data' => message }
    info = Pubnub.instance.publish({
                            'channel' => 'testing',
                            'message' => message
                          })
    puts(info)
  end
end

You could also make it a class variable, to link it more tightly to a specific model:

require 'pubnub'    
class Message < ActiveRecord::Base
    @@pubnub_obj = Pubnub.new('xyz', 'xyz', 'xyz', 'xyz')

  def self.send_new_message_client(message)
    message = { 'some_data' => message }
    info = @@pubnub_obj.publish({
                            'channel' => 'testing',
                            'message' => message
                          })
    puts(info)
  end

end

Upvotes: 5

alf
alf

Reputation: 18550

In Rails, objects are recreated on each request. If this is some kind of service, it should be a singleton in the scope of a request.

Singleton objects should be created with the ruby singleton mixin:

require 'singleton'

class Pubnub
  include Singleton

  def initialize(publish_key, subscribe_key, secret_key, ssl_on)
    # ...
  end

  def publish
    # ...
  end
end

Then you can call it with the instance method:

Pubnub.instance.publish

This way you make sure that this object will actually be a singleton (only one instance will exist).

You can place it safely in the models directory, though I often prefer the lib directory or maybe create a new directory for services. It depends on the situation.

Hope it helps!

Upvotes: 41

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