From: Joel VanderWerf <vjoel@...>
Date: 2002-11-14T05:10:40+09:00
Subject: Re: Keyword arguments?

Austin Ziegler wrote:
...
> Dave & Andy also noted that you can make it so that initialize
> receives a block. Lyle recently implemented a change to the FXRuby
> code that makes the technique cleaner (in that you don't have to use
> 'self' all over the place), like so:
> 
> class Person
>   attr_accessor :name, :age
> 
>   def initialize(name = nil, age = nil)
>     @name = name
>     @age = age
>       # ... default initialization
>     yield self if block_given?
>   end
> end
> 
> me = Person.new { |who|
>   who.name = 'austin'
>   who.age = 31
> }

Cleaner, maybe, but there is a tradeoff. Both @name and @age must have 
writers for the above to work. With the other approach (block is handled 
with instance_eval), you can write:

me = Person.new {
   @name = 'austin'
   @age = 31
}

Either way, you're breaking encapsulation--by exposing writers, or by 
exposing the attrs themselves at the time of construction (only).