From: Hugh Sasse <hgs@...>
Date: 2006-10-20T02:48:04+09:00
Subject: Re: detecting data type

On Thu, 19 Oct 2006, Parv G. wrote:

> hello all,
> i'm new to ruby and need some help on what seems like a simple issue.
> 
> How do i find out if the argument passed to a method is a string or an 
> integer?

"It depends" :-)  At the most basic you could look at the class:
   x.class
and see what that gives you, but classes are open in Ruby so it
might not be the beast it was at birth.  So you really want to 
know if it has the right properties for what you are doing.  So you
could use
   x.respond_to?(:dowcase) 
but that really doesn't tell you much, because the method could be
redefined.  In short, you try not to test this sort of thing.
Searth the web for "Duck typing" for more on this issue.
> 
> Here's what i'm trying to do:
> 
> def method_test(some_arg)
>   if some_arg is string
>     #callmethod A
>   else
>     #callmethod B
>   end
> end

Not really, that's more like what you have done when trying to do 
something else.  What was your actual goal?
For this case you *could* use:

  if some_arg.respond_to?(:method_a)
    some_arg.method_a
  else
    some_arg.method_b
  end

but ideally you want to be sure that your method is called with the
correct type anyway.  You could also use some_arg.to_i, some_arg.to_s 
to convert to the correct type.
> 
> Thanks for your help.
> 
> Parv

        Hugh