From: Robert Klemme <shortcutter@...>
Date: 2013-02-16T23:53:31+09:00
Subject: Re: How do you associate the items of a collection instance with the collection in a smart Ruby way?

On Fri, Feb 15, 2013 at 11:54 PM, Jesse F. <lists@ruby-forum.com> wrote:

> I came up with the same answer. Almost the same code, except I don't
> need the Form to know which Items are its.

but you said earlier:

> Form has an each method to iterate over FormItems.

Then how do you access them (e.g. in #each) if they are created in
Form's constructor and immediately forgotten?

> They're read only, and Form
> has all the data. But Form has defaults and variables FormItems needs to
> read/write.

So FormItems are read only but they modify their container?  You could
then make them immutable.

FormItem = Struct.new :container, :data do
  def display
    puts "This is a silly example: #{data}"
    container.shown += 1
    self
  end
end

class Form
  attr_accessor :shown

  def initialize(data)
    @items = data.map {|d| FormItem[self, d].freeze}
    @shown = 0
  end

  include Enumerable

  def each(&b)
    @items.each(&b)
    self
  end
end

ff = Form.new 5.times.to_a

ff.each {|fi| fi.display}
puts ff.shown

ff.first.data = "boom"

> I was looking for something like a .Net interface. I guess I just have
> to stop fighting it.

It's always a good strategy to not expect your new programming
language to be the same as the old one. :-)

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/