From: Jeremy Bopp <jeremy@...>
Date: 2010-10-30T11:31:38+09:00
Subject: Re: Dynamically reference instance vars

On 10/29/2010 09:14 PM, Greg Willits wrote:
> If I need to dynamically reference instance vars, is this the only way
> to do it (var set example)?
> 
>   my_object.send(:instance_variable_set, "@#{iname}", ivalue)
> 
> I expected something more elegant, but this is the only way I can get it
> to work. No biggie, just curious.
> 
> More complete example below.
> 
> -- gw
> 
> 
> class Shape
>   attr_accessor :size, :fill_color, :line_color, :line_width
>   def initialize
>     @size = ""
>     @fill_color = ""
>     @line_color = ""
>     @line_width = ""
>   end
> end
> 
> my_shape = Shape.new
> 
> shape_details = {
>   :size => 'small',
>   :fill_color => 'red',
>   :line_color => 'black',
>   :line_width => '2'}
> 
> shape_details.each do |iname, ivalue|
>   my_shape.send(:instance_variable_set, "@#{iname}", ivalue)
> end

How about backing the accessors with a hash that also has an accessor?
That way you could merge in a hash of settings or set/get them neatly by
name:

class Shape
  attr_reader :details

  def initialize
    @details = {
      :size => "",
      :fill_color => "",
      :line_color => "",
      :line_width => ""
    }
  end

  def size
    @details[:size]
  end

  def size=(size)
    @details[:size] = size
  end

  def fill_color
    @details[:fill_color]
  end

  def fill_color=(fill_color)
    @details[:fill_color] = fill_color
  end

  def line_color
    @details[:line_color]
  end

  def line_color=(line_color)
    @details[:line_color] = line_color
  end

  def line_width
    @details[:line_width]
  end

  def line_width=(line_width)
    @details[:line_width] = line_width
  end
end

my_shape = Shape.new

shape_details = {
  :size => 'small',
  :fill_color => 'red',
  :line_color => 'black',
  :line_width => '2'
}

my_shape.details.merge!(shape_details)


-Jeremy