nop.rb

# A sometimes useful development utility
class Nop < BlankSlate

  def self.null
    new {}
  end

  def self.void
    new {throw :skip}
  end

  def initialize(&blk)
    @run = blk
  end

private

  def method_missing(method, *args, &blk)
    catch(:self) {
      catch(:skip) {
        @run[method, *args]
        if Object.instance_methods.include? method
          throw :self, Object.instance_method(method).bind(self).call(*args, &blk)
        end
      }
      self
    }
  end

end

nop_spec.rb

# A quick spec to verify that this idea works
# Extracted from other code of course so you might have to tweak this.
# It also assumes BlankSlate is in the environment already.

require File.dirname(__FILE__) + '/../../spec_helper'

describe Nop, '.new' do

  it 'should create a new Nop object' do
    Nop.new {}.should be_a(Nop)
  end

  it 'should take a block for method handling' do
    called = false
    n = Nop.new {|*| called = true}
    n.anything.you.want
    called.should == true
  end

  it 'should bind and dispatch to Object instance methods indirectly' do
    called = false
    n = Nop.new {|*| called = true}
    n.object_id.should == Object.instance_method(:object_id).bind(n).call
    called.should == true
  end

  it 'should allow throw :skip to skip other methods' do
    called = false
    n = Nop.new {|*| called = true; throw :skip}
    n.object_id.should == n
    called.should == true
  end

  it 'should allow throw :self to override what is returned' do
    called = false
    n = Nop.new {|*| called = true; throw :self, 42}
    n.object_id.should == 42
    called.should == true
  end

end

describe Nop, '.null' do

  it 'should return self except for object methods' do
    Nop.null.foo.bar.class.should == Nop
  end

end

describe nop, '.void' do

  it 'should always return self' do
    obj = Nop.void.foo.bar.class
    Object.instance_method(:equal?).bind(obj).call(obj).should == true
  end

end