From: Robert Klemme <shortcutter@...>
Date: 2010-03-19T23:02:22+09:00
Subject: Re: problem making an array of arrays (of arrays)

2010/3/19 Cec Tre <cecil.treadwell@gmail.com>:
> Hey, bit of a ruby noob here :)
>
> First, hello ruby-forum community.
>
> So, here is my problem. I want to create a 5x5 grid, however, each of
> the 'cells' in the grid should be able to hold a variety of values.
>
> Firstly, I started off with this:
>
>    @row_1 = ['x','x','x','x','x']
>    @row_2 = ['x','x','x','x','x']
>    @row_3 = ['x','x','x','x','x']
>    @row_4 = ['x','x','x','x','x']
>    @row_5 = ['x','x','x','x','x']
>    @grid = [@row_1,@row_2,@row_3,@row_4,@row_5]
>
> So, obviously this creates a 5x5 grid, in which each of the 'cells' or
> @row_1..5[1..5] == 'x'.
>
> I used to just alter the string value in each cell by using:
>
>    @grid[y][x] = 'new string'
>
> But, I ultimately want each cell to be an array.. So that I can push and
> pop their values as they change, and then the grid will always display
> the last value in the array, by using:
>
>    @row_1 = [array.last,array1.last,array2.last,array3.last]
>    #etc etc etc...
>
> My problem then is, that I have a different variable name for each of
> the five points in each of the five rows.
>
> So, the solution I really want is:
>
> Is it possible to have a variable called, say... cellxx ... Then, some
> piece of code that alters the xx part of the actual variable name
> itself?
>
> Because, I'm going about implementing cell00, cell01, cell02, cell03 etc
> etc each as an array and my code is getting messy.

It's not a good idea to encode what is an index into the variable
name.  Rather you should use proper indexing.

> Please is there an (easier) way, to do what I want?

grid = Array.new(5) { Array.new(5) { [] } }

Now you can do

irb(main):006:0> grid[1][2]
=> []
irb(main):007:0> grid[1][2] << "dat"
=> ["dat"]
irb(main):008:0> grid[1][2]
=> ["dat"]
irb(main):009:0> grid[1][2] << "foo"
=> ["dat", "foo"]
irb(main):010:0> grid[1][2]
=> ["dat", "foo"]

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
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