From: Robert Klemme <shortcutter@...>
Date: 2009-10-27T19:15:45+09:00
Subject: Re: [QUIZ] Enumerable ObjectSpace (#222)

2009/10/27 Stefano Crocco <stefano.crocco@alice.it>:
> On Saturday 24 October 2009, Daniel Moore wrote:
> Here's my solution. It uses an instance variable to keep trace of the argument
> given to the enumerable method.

Instance variables are not thread safe.  I am using a thread local instead:

#! ruby19

# CODE

class <<ObjectSpace
  include Enumerable

  def arg(a, &b)
    stack = Thread.current[:_os_arg_] ||= []
    stack.push a

    begin
      instance_eval(&b)
    ensure
      stack.pop
    end
  end

  def each(&b)
    a = ((Thread.current[:_os_arg_].last || Object) rescue Object)
    each_object(a, &b)
    self
  end
end

# TEST

Foo = Struct.new :x
foos = (1..10).map {|i| Foo.new i}

result_test = ObjectSpace.arg Foo do
  p map {|x| x.inspect}

  ObjectSpace.arg String do
    string_count = inject(0) do |sum, o|
      raise "no string" unless String === o
      sum + 1
    end

    puts "Nested String count: #{string_count}"
  end

  map {|x| "rt #{x.inspect}"}
end

p result_test

Thread.new do
  p ObjectSpace.inject(0) {|sum,| sum + 1}
end.join

ObjectSpace.arg Foo do
  p map {|x| x.class}
end

Cheers

robert

-- 
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