Another way for global variable in Ruby and Sinatra

Question

I am using Ruby and Sinatra for my application.

I want to assign a variable which will be used in different classes and methods.

In my app file ie 'Millennium' is my app name so the application file is millennium.rb contains :

require 'rubygems'
require 'sinatra'
require 'yaml'
require 'active_record'
require 'sidekiq'
require 'statsd'

custom_statsd = Statsd.new('localhost', 8125)  #custom_statsd available across the application. 

class Millennium < Sinatra::Application
  set :use_queueing_in_dev, false # useful for debugging queue issues.
  set :protection, :except => [:json_csrf]

  configure do
    # These allow our error handlers to capture the errors
    disable :raise_errors
    disable :show_exceptions
    enable :logging
  end

  before do
    #logger.info request.body.read
    request.body.rewind
  end
end

Here I want to use value of custom_statsd variable in any class of my application.

I think using "$" is not a good idea. Please suggest me what is the other way to do this.

Thanks!!!!

Answer 1

It might be marginally better to put the instance in a class variable in a shared config module, like so:

module MyAppConfig
  def self.statsd
    @statsd ||= Statsd.new('localhost', 8125)
  end
end

class SomeOtherThing
  def log!
    MyAppConfig.statsd.something('hey')
  end
end

SomeOtherThing.new.log!

Answer 2

Using a global variable in general is not recommended but in certain circumstances it is the simplest so the best way, just don't overuse it. I recommend using a single constant as a namespace here, initialised from a yaml config file.

CONFIG = YAML::load_file("./config.yaml")

to_monitor CONFIG.monitor.osign_job_id

here the config.yaml

--- !ruby/struct
  zf: 999
  debug_level: DEBUG # available log levels are: DEBUG, INFO, WARN, ERROR and  FATAL 
  :monitor: !ruby/struct
    osign_job_id: 86