From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2009-10-03T00:28:29+09:00
Subject: Re: operating on a selection of objects

On Fri, Oct 2, 2009 at 4:54 PM, James French
<James.French@naturalmotion.com> wrote:
> Hi,
>
> I want to be able to do operations to a selection of objects, something like this:
>
> class Config
>  attr_accessor :name
> end
>
> class ConfigSelection
>
>  def initialize(*configs)
>    @configs = configs
>  end
>
>  def name=(n)
>    @configs.each{|c| c.name = n}
>  end
>
> end
>
> a = Config.new
> a.name = "a"
>
> b = Config.new
> b.name = "b"
>
> s = ConfigSelection.new(a, b)
> s.name = "s"
>
>
> I was wondering if there might be a more elegant way of doing this, without having to explicitly duplicate all of Config's attributes in ConfigSelection?

This is a way, with the restriction that it only checks instance
methods defined in the class:

irb(main):015:0> c = Config.new
=> #<Config:0xb7db3f78>
irb(main):016:0> c.name="test"
=> "test"
irb(main):017:0> c2 = Config.new
=> #<Config:0xb7dad038>
irb(main):018:0> c2.name = "test2"
=> "test2"

irb(main):041:0> class ConfigSelection
irb(main):042:1> def method_missing meth, *args, &blk
irb(main):043:2> if Config.instance_methods.include? meth.to_s
irb(main):044:3> @configs.each {|c| c.send meth, *args, &blk}
irb(main):045:3> else
irb(main):046:3* super
irb(main):047:3> end
irb(main):048:2> end
irb(main):049:1> end
=> nil
irb(main):050:0> csel = ConfigSelection.new c,c2
=> #<ConfigSelection:0xb7d9c198 @configs=[#<Config:0xb7db3f78
@name="test">, #<Config:0xb7dad038 @name="test2">]>
irb(main):051:0> csel.name="changed"
=> "changed"
irb(main):052:0> csel
=> #<ConfigSelection:0xb7d9c198 @configs=[#<Config:0xb7db3f78
@name="changed">, #<Config:0xb7dad038 @name="changed">]>

Hope this gives you some ideas,

Jesus.