From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2009-01-12T18:02:48+09:00
Subject: Re: Dynamically created attributes

On Mon, Jan 12, 2009 at 9:25 AM, Peter Marks <petertmarks@gmail.com> wrote:
> I'd like to specify a quantity of object attributes when creating an
> instance of an object. For example, I would like to create a Grid object
> with 4 different 'row' attributes like this: Grid.new(4). Here's some
> dirty code that does that:
>
> class Grid
>  #Creates row1, row2, etc. depending on row arg
>  def initialize(rows)
>    row_count = 1
>    rows.times do
>      instance_eval "@row#{row_count} = 'xxx'"
>      row_count += 1
>    end
>  end
> end
>
> It's dirty, but it creates the attributes. I don't see how to
> dynamically create accessor methods for all these attributes though. Any
> suggestions? I sense there's a better way to do this.
> --
> Posted via http://www.ruby-forum.com/.
>
>

Maybe this is cleaner:

class Object
	def singleton_class
		class << self; self; end
	end
end

class Grid
	def initialize rows=0
		rows.times do |i|
			instance_variable_set "@row#{i}", "initial value"
			singleton_class.instance_eval {attr_accessor "row#{i}"}
		end
	end
end

irb(main):020:0> a = Grid.new 3
=> #<Grid:0xb7c02008 @row0="initial value", @row2="initial value",
@row1="initial value">
irb(main):021:0> a.methods.grep /row/
=> ["row0", "row0=", "row1", "row1=", "row2", "row2="]

Hope this helps,

Jesus.