From: Tom Kos <lists@...>
Date: 2013-03-07T06:15:10+09:00
Subject: Coupling vs providing dependencies in Ruby

I'm java programmer diving into Ruby language (not rails stuff). Looking
at ruby codebases I see a lot of code like this
https://gist.github.com/anonymous/5101448.

Take a look at the SchedulerJob definition:

class SchedulerJob

  def run
    expired_requests = RequestSchedule.new.fetch_all_expired
    RequestToQueuePusher.new.enqueue(expired_requests)
  end

end

It explicitly creates RequestSchedule and RequestToQueuePusher. Those
two objects are plain stateless "services". This code works fine, but
for me it introduces very high coupling between SchedulerJob and those
classes. In Java we'd normally inject their instances in constructor and
don't use "new" inside to create them.
I'm not sure why this is not popular technique in Ruby. I was trying to
google for that and all I got can be told as "Ruby doesn't need
dependencies injection". Why is it so? I know stubbing RequestSchedule
or RequestToQueuePusher for tests is easy (with rspec e.g.), but
testability is not the only point.
Is this really Ruby way for OOP? For me it breaks SOLID principles I
know. I'd like to code in Ruby the Ruby way but it seems to be
completely different than in Java, and I thought OOP concepts and
practices should not vary between languages.

How do you approach such situations, or you don't care and just put
"new" every time you want to reach dependent object?

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