From: transfire@...
Date: 2006-07-04T19:48:31+09:00
Subject: InterfaceFilter as better BlankSlate (was: About 1.9 #__method__ feature)


Yukihiro Matsumoto wrote:

> #method_missing is and will be called when you invoke private methods
> with the receiver specified.

Great! Thank you..

I have come up with the following implementation as a more flexible
solution to BlankSlate. I called it InterfaceFilter for lack of a
better name. I see one prbolem though. It cannot react dynmically when
a new method is added to an ancestor. While, it would make sense if
#method_added triggered the same callback in effected sublasses, I
suppose that's too much overhead. Still, is their anyway to achieve
dynamic behavior here?

T.


module InterfaceFilter

  ESSENTIAL = [ 'funcall', 'send', 'object_id', 'object_class'
'equal?', '==', 'dup', 'clone' ]
  SECONDARY = [ 'class', 'respond_to?', 'inspect', 'hash' ]
  OPERATOR  = [ /^\W$/ ]
  SHADOW    = [ /^__/  ]
  QUERY     = [ /\?$/  ]
  INSTANCE  = [ /^instance_/ ]

  DEFAULT = ESSENTIAL | SECONDARY | SHADOW | OPERATOR | QUERY

  #

  def self.included( base )
    base.const_set( 'InterfaceFilter', self )
  end

  #

  def self.[]( *patterns )
    cls = self.dup
    cls.preserve_features( patterns, public_instance_methods(true) )
    cls
  end

  #

  def self.preserve_features( patterns, methods=nil )
    patterns.flatten!
    methods ||= Kernel.public_instance_methods
    methods.each do |m|
      case m
      when *patterns
        public m
      else
        private m
      end
    end
  end

  preserve_features( DEFAULT )

end


#= begin test

  class X
    include InterfaceFilter[ InterfaceFilter::ESSENTIAL ]
  end

  x = X.new
  p X.ancestors
  p x.class
  p x.instance_variables

#=end