apply.rb - Proc を binding を変えて実行します

apply.rb

class Proc
  def apply(binding, *args)
    binding.instance_variable_set :@args, args
    binding.instance_eval do
      def method_missing varname, *args, &blk
        return if varname == :to_ary
        if !args.empty? || blk
          $temp_args = args
          $temp_blk = blk
          res = eval "#{varname} *$temp_args, &$temp_blk"
          $temp_args = nil
          $temp_blk = nil
        else
          res = eval "#{varname}"
        end
        res
      end
    end
    binding.instance_exec(*args, &self)
  end
end

if __FILE__ == $PROGRAM_NAME

  require "test/unit"

  class TestApply < Test::Unit::TestCase

    def setup 
    end

    def a_binding(&blk)
      i = 42
      blk.apply binding, "hello"
    end

    def test_apply
      a_binding { |string|
        assert_equal i, 42
        assert_equal string, "hello"
      }
    end

  end

end