From: "David A. Black" <dblack@...>
Date: 2009-10-03T03:02:13+09:00
Subject: Re: operating on a selection of objects

Hi --

On Fri, 2 Oct 2009, James French 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?

Here's a different approach from the method_missing ones, just to give
you some further ideas:

class Config
   ATTRIBUTES = [:name, :age, :email]
   attr_accessor *ATTRIBUTES
end

class ConfigSelection

   def initialize(*configs)
     @configs = configs
   end

   Config::ATTRIBUTES.each do |attr|
     define_method("#{attr}=") do |val|
       @configs.each {|c| c.send("#{attr}=", val) }
     end
   end
end


David

-- 
David A. Black, Director
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Ruby/Rails training, consulting, mentoring, code review
Book: The Well-Grounded Rubyist (http://www.manning.com/black2)