From: Mark Volkmann <r.mark.volkmann@...>
Date: 2006-03-23T06:53:03+09:00
Subject: Re: Introspection of method parameters

On 3/22/06, Keith Sader <ksader@gmail.com> wrote:
> Ok, I tried that and it gets me to where I am now, I can see the
> methods for an object, but I can't tell if the method
>
> a.) takes a parameter
> b.) if it takes a parameter the # of parameters it takes.

Both can be answered using the arity method in the class Method.

For example, how many parameters does the Math class method sin take?
puts Math.method(:sin).arity
outputs 1

How may parameters does the String instance method slice take?
String.new.method(:slice).arity
outputs -1
This is because slice takes a variable number of arguments.
In this case the return value is -n-1 where n is the number of
required arguments.
So the number of required arguments is zero.
But I don't think that's true. It looks to me like slice requires 1 argument!

> On 3/22/06, David Ishmael <dishmael@windwardcg.com> wrote:
> > Try this ...
> >
> > http://www.rubycentral.com/book/ospace.html
> >
> > -Dave
> >
>
> >
> > I'm trying to find out the number and name of a method's parameters.
> > I've googled for 'ruby method parameter introspection' and come up
> > with almost nothing.  Is there a way to ask a method for the
> > parameters it takes?
> >
> > Could this way also show me the method overloads?
> > foo()
> > foo(param1)
> > foo(param1, param2)
> > etc.
> >
>
> thanks,
> --
> Keith Sader
> ksader@gmail.com
> http://www.saderfamily.org/roller/page/ksader
>
>


--
R. Mark Volkmann
Object Computing, Inc.