From: "Mauricio Fernández" <batsman.geo@...>
Date: 2004-01-14T17:15:58+09:00
Subject: Re: What object-configuration approach to use?

On Wed, Jan 14, 2004 at 02:07:43PM +0900, Gavin Sinclair wrote:
> > 4. YieldSelf
> >
> > I've seen some people include a "yield self" in the initialize() method,
> > which allows you to do something like this:
> >
> >     class Link
> >         attr_accessor :url, :content, ...   # this line was missing
> >         def initialize(url, content)
> >           @url = url
> >           @content = content
> >           yield self if block_given?
> >         end
> >     end
> >
> >     link = Link.new(url, "here") { |l|
> >         l.title = "the whole story"
> >     }
>
> The only downside is that it requires you to set *accessors* instead of
> the more restrictive *readers*.

Credits go to Hal Fulton

batsman@tux-chan:/tmp$ expand -t2 a.rb
class A
  attr_reader :foo, :bar

  # only for initialize! :nodoc: or something for rdoc
  attr_writer :foo, :bar

  def initialize
    yield self
    klass = class << self; self  end
    ["foo=", "bar="].each { |m| klass.send :undef_method, m }
    self
  end
end

a = A.new do |s|
  s.foo = 1
  s.bar = 2
end

p a
a.foo = 1

batsman@tux-chan:/tmp$ ruby a.rb
#<A:0x401c8a48 @bar=2, @foo=1>
a.rb:22: undefined method `foo=' for #<A:0x401c8a48 @bar=2, @foo=1> (NoMethodError)


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