From: Adam Gardner <adam.oddfellow@...>
Date: 2009-02-26T02:37:24+09:00
Subject: Re: Infinite loop with Singleton mixin

Yukihiro Matsumoto wrote:
> Hi,
> 
> In message "Re: Infinite loop with Singleton mixin"
>     on Wed, 25 Feb 2009 13:45:41 +0900, Adam Gardner 
> <adam.oddfellow@gmail.com> writes:
> 
> |This loops inifitely, but it doesn't seem like it should.
> 
> Uninitialized singleton object should not be disclosed, I think.  So I
> think it should loop infinitely, as you specified.
> 
>               matz.

Personally, I disagree. I think both consistency and utility would be 
better served by having .instance return the instance as soon as 
initialize has started - after all, there are plenty of other ways to 
get references to objects which haven't finished their initialize 
function, and they don't cause undue trouble. But I can understand why 
it might need to be the way it is. I'll try and work around it.

Incidentally, it turns out the code above isn't looping the way I 
thought it was; it's actually stuck inside the while loop in 
singleton.rb:148-152

while false.equal?(@__instance__)
  Thread.critical = false
   sleep(0.08)   # timeout
   Thread.critical = true
end

Which, itself, suggests a work-around:

----
require 'singleton'

class SingleThing
  include Singleton
  def initialize
    self.class.instance_variable_set(:@__instance__,self)
    @a = OtherThing.new
  end
end

class OtherThing
  def initialize
    @single_ref = SingleThing.instance
  end
end

a = SingleThing.instance
----

Anyway, thanks for your attention, and thank you for your hard work on 
Ruby.

-- 
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