From: Simon Strandgaard <neoneye@...>
Date: 2003-12-01T02:22:09+09:00
Subject: Re: selfassignment and close

On Fri, 28 Nov 2003 14:54:59 -0700, Ara.T.Howard wrote:

> On Fri, 28 Nov 2003, Simon Strandgaard wrote:
>> I would like to overload the '+=' operator. But it doesn't seems to be
>> possible?    If it isn't possible, then how to use the '+' operator and at
>> the same time get the instance #closed correctly ?
[snip code]
> 
> if you rely on ObjectSpace.define_finalizer you don't really know when the
> call will be made, but perhaps something using it would be better...  this
> would cause an apparent 'leak' in long running programs.  the general idea -
> track objects within the class itself and make sure to free them - should be
> workable for you though.

I had something similar, a WrapperIterator which kept track of all clones.
When the operation were completed, I could then sweep them.
But I don't consider it as a 'real' solution :-)

It has to be solved _correct_, before im satisfied.

--
Simon Strandgaard



server> expand -t2 wrapper_close.rb 
require 'iterator'  # http://raa.ruby-lang.org/list.rhtml?name=iterator

class Scanner
  def initialize(iterator)
    @iterator = iterator
  end
  def execute
    a = @iterator.clone
    b = @iterator.clone
    c = @iterator.clone
    d = @iterator.clone
  end
end

# keep track of how many instances we have
class CountingIterator < Iterator::Collection
  @@count = 0
  def clone
    @@count += 1
    super()
  end
  def self.count; @@count end
  def close
    @@count -= 1
    super()
  end
end

class WrapperIterator < Iterator::Base
  def initialize(iterator, stack=nil)
    @iterator = iterator
    @stack = stack || []
  end
  def clone
    i = @iterator.clone
    @stack << i
    WrapperIterator.new(@iterator, @stack)
  end
  def close
    @stack.map{|i| i.close; nil}
  end
end

ary = (0..19).to_a
iterator = CountingIterator.new(ary)
#wrap_iterator = iterator
wrap_iterator = WrapperIterator.new(iterator)
s = Scanner.new(wrap_iterator)
s.execute
p CountingIterator.count
wrap_iterator.close # ensure all iterators gets closed
p CountingIterator.count
server> ruby wrapper_close.rb 
4
0
server>