From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2013-06-06T21:55:12+09:00
Subject: Re: Playing with method_missing -- argument list

On Thu, Jun 6, 2013 at 2:15 PM, Tamara Temple <tamouse.lists@gmail.com> wrote:
>
> In https://gist.github.com/tamouse/5719507 , I've been playing around
> with using Struct, Enumerable, Comparable and lastly method_missing, and
> here's where I got stuck.
>
> At lines 67-69 ("This is going to be fun"), I collect the instance
> methods defined in each of Array, Hash, and String, to be able to pass
> them along to each of the components of MyClass.
>
> The problem now comes, how many arguments do I pass along as well?
>
> My test example, #keys from Hash, shows my problem. #keys takes no
> arguments, but even if the argument list is empty, it's an empty Array,
> which of course is something. In some contexts this might be fine, but
> in others, not so much.
>
> So, is there a way to detect the number of arguments a method takes?
>
> Or, would it be better to detect the size of args at that point and send
> zero, one or many to the attribute's method? Thinking something like:
>
> def check_size(args)
>   case args.size
>   when 0 ; nil
>   when 1 ; args.first
>   else args
> end
>
> (only maybe not so weak a method name)
>
> AND, is this already a standard function/idiom?
>


I think you should be calling send with *args:

2.0.0p195 :001 > h = {}
 => {}
2.0.0p195 :002 > args = []
 => []
2.0.0p195 :003 > h.send(:keys, *args)
 => []
2.0.0p195 :004 > h = {:a => 3}
 => {:a=>3}
2.0.0p195 :005 > h.send(:keys, *args)
 => [:a]

Jesus.