From: Mike Sassak <msassak@...>
Date: 2009-07-01T01:18:31+09:00
Subject: Re: attr_writers within blocks

--0016e6476e76360af0046d9328d7
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

Hi David,

On Tue, Jun 30, 2009 at 8:01 AM, David A. Black <dblack@rubypal.com> wrote:

> Hi --
>
> On Tue, 30 Jun 2009, Mike Sassak wrote:
>
>  On Mon, Jun 29, 2009 at 2:44 PM, Wijnand Wiersma <wijnand@videre.net>
>> wrote:
>>
>>  Hi all,
>>>
>>> It seems writer methods don't work within blocks, the names are resolved
>>> to
>>> new local variable names I guess.
>>> It is funny however the reader method does seem to work fine.
>>> Is it possible to make it work anyway  without changing the syntax within
>>> the block?
>>>
>>> My example gist: http://gist.github.com/137741
>>>
>>>
>> You can override the getter method for a DSL-ish syntax:
>>
>
> Assuming your DSL depends on the lack of equal-signs :-) There's
> nothing inherent in the concept of a DSL that disallows =-terminated
> methods or explicit receivers.
>

Of course! I was thinking of ActiveRecord's macro method syntax--not the
most apropos when the original question was about variable assignment, I
know. :-)


>
>  class Foo
>>  attr_accessor :bar
>>
>
> No point defining #bar if you don't want it -- just use attr_writer.
>
>   def initialize(&block)
>>   instance_eval(&block)
>>  end
>>
>>  def bar(v=nil)
>>   v ? @bar = v : @bar
>>  end
>>
>
> That won't allow you to (re)set @bar to nil or false, though. You
> might want something like:
>
>  def bar(*v)
>    unless v.empty?
>      @bar, = v
>    end
>    @bar
>  end
>

 Ahh, yes. Thanks for pointing that out. I was really more concerned at the
time with giving an (admittedly idiosyncratic) example of assignment without
an explicit receiver as food for the OP's thought. I'd never thought to use
@bar, = v in order to grab only the first element of an array though. Cool!

Thanks again,
Mike


>
>
> David
>
> --
> David A. Black / Ruby Power and Light, LLC
> Ruby/Rails consulting & training: http://www.rubypal.com
> Now available: The Well-Grounded Rubyist (http://manning.com/black2)
> "Ruby 1.9: What You Need To Know" Envycasts with David A. Black
> http://www.envycasts.com
>
>

--0016e6476e76360af0046d9328d7--