From: Dave Thomas <Dave@...>
Date: 2001-09-04T16:37:26+09:00
Subject: [ruby-talk:20841] Re: modify hash during iteration

Tomas Brixi <brixi@unicode.cz> writes:

> Hello
> 
> I have a question to following piece of code
> -----------------
> h = Hash.new
> #assign some data
> 
> h.each do |pair|
>     h[pair[0]] = new_value
> end
> -----------------
> 
> is this the right way or are there better ways to do this

I'm not sure what you're asking about. If it's the pair[0] call, then
you could do

  h = {  "cat" => 1, "dog" => 99 }

  h.each do |key, |
    h[key] += 1
  end


If instead you're asking about what happens if you modify the keyset
of the hash, not the values, your iterations may not cover the entire
original hash:

  h = { 1 => :one, 2 => :two, 3 => :three }

  h.each do |key, value|
    puts "#{key} => #{value}"
    h.delete key+1
  end

 #=>

  1 => one
  3 => three


Regards


Dave