From: Michael Guterl <mguterl@...>
Date: 2008-08-02T12:48:30+09:00
Subject: Re: Ruby block: why doesn't this work?

On Fri, Aug 1, 2008 at 11:04 PM, markbuckingham@gmail.com
<markbuckingham@gmail.com> wrote:
> I'm trying to figure out why my code isn't doing what I think it
> should...
>
> Basically, I'm trying to create a Info object, and do various things
> to that new object within the block.  For what ever reason though, it
> doesn't look like the code inside the block is getting executed at
> all.  (I'm trying to do something that looks kind of like
> activerecord's create_table method.)
>
> So... with the print statements in the code, I'd expect to see output
> from the address() and city() methods, but only the initialize method
> prints anything.  (I can even put complete nonsense in the address or
> city methods, and nothing happens.)
>
> What am I doing wrong?
>
You need to make the info method call the block.  See the code below.

> Thanks!
>
> class Info
>  attr_accessor :name, :address, :city
>
>  def initialize(name)
>    @name = name
>    print "name: #{name}\n"
>  end
>
>  def address(value)
>    @address = value
>    print "address: #{address}\n"
>  end
>
>  def city(value)
>    @city = value
>    print "city: #{city}\n"
>  end
> end
>
> def info(name)
     i = Info.new(name)
     yield i
     i
> end
>
> info :Bob do |i|
>  i.address "123 Main St."
>  i.city "Boston, MA"
> end
>
Also this code will currently give you errors because attr_accessor is
overwriting your existing method definitions.  I recommend using the
'fattr' gem it will give you most of the functionality you desire.

HTH,
Michael Guterl
require 'rubygems'
require 'fattr'

class Info
  fattr :name, :address, :city

  def initialize(name)
    self.name = name
  end
end

def info(name)
  i = Info.new(name)
  yield i
  i
end

bob = info 'bob' do |i|
  i.address "123 foo lane"
  i.city "oz"
end

puts bob.inspect