Vital Ruby Lab 5

read_only_proxy.rb

class ReadOnlyProxy
  def initialize(target)
    @target = target
  end

  def method_missing(sym, *args, &block)
    if sym.to_s !~ /=$/
      @target.send(sym, *args, &block)
    end
  end
end

read_only_proxy_test.rb

require 'test/unit'
require 'read_only_proxy'

class ReadOnlyProxyTest < Test::Unit::TestCase
  class Thing
    attr_accessor :name
  end

  def setup
    super
    @thing = Thing.new
    @thing.name = "THING"
    @ro = ReadOnlyProxy.new(@thing)
  end

  def test_creating_proxy
    assert_not_nil @ro
  end

  def test_normal_methods_pass_thru
    assert_equal "THING", @ro.name
  end

  def test_writing_methods_are_blocked
    @ro.name = "HACKED"
    assert_equal "THING", @thing.name
  end
end

shadow_proxy.rb

class ShadowProxy
  def initialize(target)
    @target = target
    @shadow = {}
  end

  def method_missing(sym, *args, &block)
    name = sym.to_s
    if sym.to_s =~ /=$/
      name.gsub!(/=$/,'')
      @shadow[name] = args.first
    elsif @shadow.has_key?(name)
      @shadow[name]
    else
      @target.send(sym, *args, &block)
    end
  end
end

shadow_proxy_test.rb

require 'test/unit'
require 'shadow_proxy'

class ShadowProxyTest < Test::Unit::TestCase
  class Thing
    attr_accessor :name
  end

  def setup
    super
    @thing = Thing.new
    @thing.name = "THING"
    @sh = ShadowProxy.new(@thing)
  end

  def test_creating_proxy
    assert_not_nil @sh
  end

  def test_normal_methods_pass_thru
    assert_equal "THING", @sh.name
  end

  def test_writing_methods_are_blocked
    @sh.name = "HACKED"
    assert_equal "THING", @thing.name
  end

  def test_writing_methods_are_shadowed
    @sh.name = "HACKED"
    assert_equal "HACKED", @sh.name
  end

end