From: Alexey Petrushin <axyd80@...>
Date: 2011-10-31T03:42:28+09:00
Subject: How to save method signature while wrapping it?

Hello, it would be interesting to automatically destruct hashes into
named method arguments, Ruby has the Method.parameters method:

    class A
      def my_method a, b, c = 10; end
      p instance_method(:my_method).parameters
      # ==> [[:req, :a], [:req, :b], [:opt, :c]]
    end

So, You can use this method signature to automatically destruct hash
into named arguments, something like this:

    A.new.send_with_params :my_method, a: 'a', 'b': 'b'

And it works. But, there's a problem - all this is broken when You wrap
method (like `alias_method_chain` or some other way) - the signature of
the original method is losted:

    class A
      alias_method :my_method_without_feature, :my_method
      define_method :my_method do |*args|
        my_method_without_feature *args
      end
      p instance_method(:my_method).parameters
      # ==> [[:rest, :args]]
    end

So, I'm wondering, maybe there's some way to wrap method and still
preserve its signature?

Basically attribute names are available (from method.parameters), but I
don't know how to express named attributes in
block signature, i.e. - how to dynamically write `... do |args[1],
args[2], args[3]|` instead of `... do |*args|` (without eval of course
:) ).

Thanks, Alex.
http://petrush.in

P.S. if someone interested how to do :send_with_params here's full code
and specs (search for send_with_params keyword):
https://github.com/alexeypetrushin/ruby_ext/blob/master/lib/ruby_ext/core/object.rb
https://github.com/alexeypetrushin/ruby_ext/blob/master/spec/core/object_spec.rb

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