From: Caleb Clausen <vikkous@...>
Date: 2006-07-28T04:10:44+09:00
Subject: Re: Symbols are your friends

On 7/27/06, Daniel Schierbeck <daniel.schierbeck@gmail.com> wrote:
> > (You're prepending "to_" to your method names before checking; I don't
> > know why. This way seems more general....)
>
> I was using it to demonstrate how you could duck type check with a case
> statement, so focusing on the "type" made sense. I see this all the time:
>
>    case obj
>      when Integer then foo
>      when String then bar
>    end
>
> and it strikes me as not being very duckish (quacky?) Using if
> statements can be annoying:
>
>    if obj.respond_to? :to_str
>      foo
>    elsif obj.respond_to? :to_int
>      bar
>    end

I see where you're coming from, but I guess I just don't see that
#to_* methods as being that special. Why wouldn't you want to do this
kind of dispatch for other methods too?

Using the code I posted previously, the above conditionals could be written as:

case obj
when -:to_str
  foo
when -:to_int
  bar
end

I like that one best.

Fooling with the existing Symbol#=== in any way is very likely to
break some existing libs which assumes the current definition always
obtains... my way lets you use (almost-)symbols in the way you want to
use them. It is incompatible with libs that also define Symbol#-@ in a
different way, but those are presumably much rarer, perhaps
nonexistant. (Nobody's as crazy as I am.) If you really want this
feature in a general way, (and I do, for Reg) this seems to be the
best compromise.