From: Rob Biedenharn <Rob@...>
Date: 2008-09-20T07:46:03+09:00
Subject: Re: overwriting hash key

On Sep 19, 2008, at 6:37 PM, jim wrote:

> How can get Ruby to tell me when I'm overwriting an existing key in my
> hash?
>
> For example,
>
>   h = { "key1" => [6, 44, 12],
>         "key2" => [8, 1],
>          .
>          .
>       }
>
> The hash could get big enough where I accidentally add a new entry,
>
>         "key1" => [99, 3]
>
> when what I needed to do was add [99, 3] to key1's array. I won't get
> any warning that the first occurrence of key1 is being replaced.

Well, if you always have arrays for the values, you can start with:

  h = Hash.new {|h,k| h[k] = []}

Then initialize your hash with:

  h.update({ "key1" => [6, 44, 12],
             "key2" => [8, 1],
             ...
           })

Then you can:
   h["key1"] << 99 << 3
   h["key1"].concat([99, 3])
   h["key1"].push(99, 3)

h["key1"] has [6,44,12,99,3]

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com