Singleton in scope of a request in rails [closed]

Question

Using singleton mixin from rails I could create a singleton class in the scope of rails app. But I was wondering Is there a way to create it in the scope of a particular request ?

Answer 1

Since a request is tied to a thread, you can use Thread local store:

class RequestSingleton
  def self.instance
    Thread.current['request-singleton'] ||= RequestSingleton.new
  end

  def self.clear
    Thread.current['request-singleton'] = nil
  end
end

Usage:

def index
  RequestSingleton.instance.do_some_setup

  # ...

  RequestSingleton.clear
end

...and anywhere else simply use RequestSingleton.instance to access it.

Since it is thread local, there are no synchronization issues.