From: Harry Ohlsen <harryo@...>
Date: 2003-08-28T17:37:08+09:00
Subject: Re: getting the arity

Jeff Mitchell wrote:

> Hi,
> 
> I would like to get the arity of a method.  However, arity is a method
> of Method, and I can only get a Method from the method method of Object
> (phew!).
> 
> So it appears impossible to get the arity of a method in a class
> without making an instance of that class.  Is this true?
> 
> A hypothetical use would be to print out all classes with their arity
> at a given time during execution (and making dummy instances could
> cause unwanted side-effects).

Here's a starting point.  Note that, of course, you get a lot more methods than you bargained for, because it will show you all the inherited methods, too.

Hope it helps.

---------------

def dump_methods(klass)
   klass.methods.each do |name|
      method = Fred.method(name)

      puts "#{name} arity #{method.arity}"
   end
end

class Fred
   def f(a, b, c)
   end

   def g(x)
   end
end

dump_methods Fred