From: "Jörg W Mittag" <JoergWMittag+Usenet@...>
Date: 2009-06-17T17:50:06+09:00
Subject: Re: Ruby Reflection Method Parameters

Phrogz wrote:
> On Jun 16, 5:13�pm, Sirisha Pusapati <pusapatisiri...@yahoo.com>
> wrote:
>> I have a class called ClassFromString and it has a method called
>> getCounterValue. It takes a parameter called name. Is there in Ruby
>> using reflection to get the name of the parameters of a method.
> There is not.

<bill-clinton>That depends on what your definition of "is"
is.</bill-clinton>

You are wrong, in so far as Proc#parameters does exist in Ruby 1.9.2.
You are right, in so far as Ruby 1.9.2 doesn't exist (yet).

See: <https://GitHub.Com/RubySpec/MatzRuby/blob/trunk/proc.c#L694-710>

> The closest you can get is a hack that reads in source
> files (if you know where they are, and they're pure Ruby

... and they exist at all (i.e. the method was not created using eval
or define_method)

> ) and either
> parses the raw code or looks at the abstract syntax tree.

Here is how the Merb-Action-Args Plugin for Merb does it:

JRuby: <https://GitHub.Com/WyCats/Merb/blob/master/merb-action-args/lib/merb-action-args/jruby_args.rb>
(using JRuby's own runtime reflection)

MRI: <https://GitHub.Com/WyCats/Merb/blob/master/merb-action-args/lib/merb-action-args/mri_args.rb>
(using ParseTree)

For all others, it tries to use the MethoPara Gem, which, however,
only works on YARV 1.9.1 (and *not* on Ruby 1.9.1, as the README
incorrectly claims!): <https://GitHub.Com/Genki/MethoPara/>

jwm