From: "Ara.T.Howard" <ahoward@...>
Date: 2003-11-29T08:27:12+09:00
Subject: Re: selfassignment and close

On Fri, 28 Nov 2003, Simon Strandgaard wrote:

> Date: Fri, 28 Nov 2003 20:24:58 +0100
> From: Simon Strandgaard <neoneye@adslhome.dk>
> Newsgroups: comp.lang.ruby
> Subject: selfassignment and close
> 
> 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 ?
> 
> 
> server> ruby a.rb
> open 42
> open 43
> close 42
> close 43
> -----------------------
> open 42
> open 43
> close 43
> server> expand -t2 a.rb 
> class Iterator
>   def initialize(value)
>     @value = value
>     puts "open #{@value}"
>   end
>   def close
>     puts "close #{@value}"
>   end
>   def +(n)
>     self.class.new(@value + n)
>   end
> end
> 
> a = Iterator.new(42)
> b = a + 1
> a.close
> b.close
> 
> puts "-----------------------"
> 
> a = Iterator.new(42)
> a += 1   # Question:  How to do selfassignment ?
> a.close
> # 42 never gets closed!
> server>


something like this:


class Iterator
  class << self
    def objs; @objs ||= []; end
    def reap; objs.each{|obj| obj.close}; end
    def new(*args,&block); objs << (obj = super); obj; end 
    at_exit { Iterator.reap }
  end
  def initialize(value)
    @value = value
    puts "open #{@value}"
  end
  def close
    puts "close #{@value}" unless @closed
    @closed = true
  end
  def +(n)
    self.class.new(@value + n)
  end
end

#a = Iterator.new(42)
#b = a + 1
#a.close
#b.close

puts "-----------------------"

a = Iterator.new(42)
a += 1   # Question:  How to do selfassignment ?
a.close
# 42 never gets closed!


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.

food for thought...

-a
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