From: Madan Manoharan <madan.manoharan@...>
Date: 2006-05-19T22:58:28+09:00
Subject: Question on GC

Hello Rubyists:

Does Ruby's GC treat a class variable (@@x) as 'global scope' or as
'local scope'?

Here is my situation:

I have a class variable that holds instances of 'self'. These objects
are not referenced any where else; these objects are retrieved using
its __id__ which is stored else where. It is my understanding that
Ruby's GC doesn't see these stored __id__ as a reference to the
objects (since __id__ -> Fixnum).

I don't want these objects to be garbage collected as long as its
instance is referred the class variable. Please note that the objects
are not referenced by other class's objects.

Example:

class Test
  @@x = []

  def initialize()
    # among other thing ...
    @@x.push(self)    if not @@x.include?(self)
  end

  def kill_self()
    # among other things
    @@x.delete(self)
  end
end

class TestFactory
  @store = []

  def getATest()
      procObj = Proc.new do |id|
        @store.delete(id)
      end

      t = Test.new()
      @store.push(t.__id__)

      ObjectSpace.define_finalizer(t, procObj)
      return t.__id__
  end

  def releaseTest(id)
      _id2Obj(id).kill_self()     # <--- retrieves Obj from __id__
  end

end

testF = TestFactory.new()
id = testF.getATest()
.......
.......
# I don't want 't' to be garbage collected here. GC.disable is not an option
.......
.......
testF.releaseTest(id)

__END__

Questions:

(1) Will 't' be garbage collected since the only reference to 't' is
in @@x, which could go out of scope?
(2) Is my understanding 'scope' correct?

Any help will be greatly appreciated.

Thanks,
-Madan.