From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2009-10-24T16:06:30+09:00
Subject: Re: Setting attribute via send in Ruby 1.8.6

On Fri, Oct 23, 2009 at 6:40 PM, Charles Calvert <cbciv@yahoo.com> wrote:
> On Fri, 23 Oct 2009 17:18:22 +0200, Robert Klemme
> <shortcutter@googlemail.com> wrote in
> <7kdvpuF37n3jvU1@mid.individual.net>:
>
>>On 10/23/2009 05:10 PM, Charles Calvert wrote:
>>> Using Ruby 1.8.6.
>>>
>>> I've run into an instance in which I'd like to set attributes of an
>>> instance using the send method.  I've looked around, but found
>>> nothing, most likely because I'm using the wrong search terms.
>
> [snip example]
>
>>> I get the following error: "wrong number of arguments (1 for 0)
>>> (ArgumentError)"
>>>
>>> Am I correct in thinking that this is possible, and that I'm just
>>> going about it the wrong way?
>>
>>Yes.
>>
>>...
>
> The suspense almost killed me!
>
>>:-)
>>
>>You need to use the _setter_ method with #send - which happens to be
>>called "foo=" in your case.
>
> Ah, now the lightbulb goes off.  I should have remembered the
> convention of having the setter have an equals sign as part of the
> name.  I'm too used to languages that determine which accessor is used
> based on which side of the assignment it appears rather than actually
> using a method name to syntactically simulate assignment.

You can achieve what you want if instead of using attr_writer you roll your own.
I remember a discussion in this list regarding something like:

class A
  def a *args
    return @a if args.empty?
    @a = args[0]
  end
end

a = A.new
a.a      #=> nil
a.a 4   #=> 4
a.a      #=> 4

With this you can do a.send(:a, 4)

Jesus.