From: Todd Benson <caduceass@...>
Date: 2007-07-12T07:04:38+09:00
Subject: Re: Accessing a specific index in a nested array

On 7/11/07, Pieter Mans <tybriel@gmail.com> wrote:
> Florian Gross wrote:
> >> For example, this works:
> >> irb> array[2]
> >> => [2, 2, 2, 2, 2, 2, 2, 2, 2, 2]
> >>
> >> But this doesn't seem to:
> >> irb> array[2[2]]
> >> => [2, 2, 2, 2, 2, 2, 2, 2, 2, 2]
> >>
> >> I'm pretty sure I'm just getting the syntax wrong.
> >
> > Yup, you're calling [] on the number 2. You want array[2][2].
>
> Thanks! That worked nicely. I'm getting a weird problem when setting
> values tho. When I try to set the value of an item in a nested array, it
> sets the value in all the other nested arrays too:
>
> irb> test = Map.new(5,5)
> => #<Map:0x2dfd7dc @coords=[["#", "#", "#", "#", "#"], ["#", "#", "#",
> "#", "#"], ["#", "#", "#", "#", "#"], ["#", "#", "#", "#", "#"], ["#"
> , "#", "#", "#", "#"]]>
> irb> test.coords[1][1] = 0
> => 0
> irb> test.coords
> => [["#", 0, "#", "#", "#"], ["#", 0, "#", "#", "#"], ["#", 0, "#", "#",
> "#"], ["#", 0, "#", "#", "#"], ["#", 0, "#", "#", "#"]]
>
> Any idea what I'm doing wrong?

Most likely you have the same object for each element of your outside
array.  You can check by doing this:

irb> test.coords[0] === test.coords[1]  #for you, this will probably return true
=> true

Look at how your array is created.  There are a number of ways to do
it.  Here's one that's not sexy but works.

size = 5
test.coords = []
size.times { test.coords << Array.new size }

hth,
Todd