From: larsch@...
Date: 2007-09-04T18:50:13+09:00
Subject: Resource Acquisition & Cleanup

Hello Rubyists,

I am looking for a style or idiom that I can apply to a resource
management problem. I have a number of resources (objects) that I need
to release if any exception is thrown. While ensure-blocks or block
parameters work well for few resources, they get cumbersome when you
have many resources, or when the number of resources is not known.

Let's say I have something similar to this:

resources = []
n.times { |i|
   resources.push( Resource.new(i) }
}

loop {
  # do some processing on the resources
}

n.times { |i|
  resources[i].release
}

If an exception is thrown in the main processing loop, i still need to
release the resources. If an exception is thrown during construction,
i need to release the resources already succesfully created. If an
exception is thrown while releasing a resource during exception
handling, i still need to release the remaining resources.

Is there a way to do this, especially when 'n' is unknown?

Regards,
Lars