How do I create a singleton global object in rails? - ruby-on-rails-3

Question

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

Answer 1

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!

Answer 2

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