From: Bill Kelly <billk@...>
Date: 2011-01-21T21:22:01+09:00
Subject: [ruby-core:34733] Re: [Ruby 1.8-Feature#4239] Let's begin a talk for "1.8.8" -- How's needed for surviving 1.8?

Zeno,

Zeno Davatz wrote:
> 
> Do you use Hash-Interations? I don't think so. It does not
> seems so or you just started using them in Ruby 1.9.2. We
> use them at least since Ruby 1.8.6.

Since you ask: I've been using ruby on a roughly daily basis
since 1999.

Here is code from a current project where I take steps to
avoid a Hash iterator due to the potential for the Hash to
be modified during iteration:

  def close_all_catalogs
    # NOTE: sv.close_all_catalogs may switch fibers,
    # and we don't want to be iterating on @servers itself during that
    # time, else another method like add_server would get
    # "RuntimeError - can't add a new key into hash during iteration"
    svs = @servers.values
    svs.each do |sv|
      sv.close_all_catalogs
    end
  end


> Also I do not play the Lottery. I prefer consistency.

You *are* playing the Lottery in ruby 1.8 if you are modifying
a hash during iteration.

$ ruby186 -v -e "h = {:a=>123,:b=>456,:c=>789}; h.each_key {|k| p k; 3.times {|i| h[i.to_s]=i}}"
ruby 1.8.6 (2009-06-08 patchlevel 369) [i386-mswin32_71]
:a
:b
:c
"0"
"1"
"2"

$ ruby186 -v -e "h = {:a=>123,:b=>456,:c=>789}; h.each_key {|k| p k; 10000.times {|i| h[i.to_s]=i}}"
ruby 1.8.6 (2009-06-08 patchlevel 369) [i386-mswin32_71]
:a
-e:1:in `each_key': hash modified during iteration (RuntimeError)
        from -e:1


You should *not* be adding new keys to a Hash during
iteration, if you claim to value "consistency".


Regards,

Bill