Vital Ruby Lab 5

read_only_proxy.py

class ReadOnlyProxy(object):
    def __init__(self, target):
        self._target = target

    def __getattribute__(self, name):
        target = object.__getattribute__(self, '_target')
        return getattr(target, name)

read_only_proxy.rb

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

  def method_missing(sym, *args, &block)
    if ! sym.to_s.end_with?('=')
      @_target.send(sym, *args, &block)
    end
  end

  def respond_to?(sym)
    self.instance_variable_defined? "@#{sym.to_s}" || super
  end
end

shadow_proxy.py

from read_only_proxy import ReadOnlyProxy

class ShadowProxy(ReadOnlyProxy):
    def __getattribute__(self, name):
        try:
            return object.__getattribute__(self, name)
        except AttributeError:
            return ReadOnlyProxy.__getattribute__(self, name)

shadow_proxy.rb

require "read_only_proxy"

class ShadowProxy < ReadOnlyProxy
  def method_missing(sym, *args, &block)
    if sym.to_s.end_with?('=')
      self.instance_variable_set "@#{sym.to_s[0...-1]}", *args
    else
      value = self.instance_variable_get "@#{sym.to_s}"
      value || super
    end
  end
end

test.py

import unittest
from read_only_proxy import ReadOnlyProxy
from shadow_proxy import ShadowProxy

class ActualObject(object):
    def __init__(self, name="INITIAL NAME"):
        self.name = name

class ReadOnlyProxyTestCase(unittest.TestCase):
    def setUp(self):
        unittest.TestCase.setUp(self)
        self.actual = ActualObject()
        self.actual.name = "ACTUAL NAME"
        self.proxy = ReadOnlyProxy(self.actual)

    def test_attributes_pass_thru(self):
        self.assertEqual("ACTUAL NAME", self.proxy.name)

    def test_attributes_are_not_set(self):
        self.proxy.name = "PROXY NAME"
        self.assertEqual("ACTUAL NAME", self.actual.name)
        self.assertEqual("ACTUAL NAME", self.proxy.name)

    def test_unset_attribute_raise_exception(self):
        self.assertRaises(AttributeError, lambda: self.proxy.unset_attr)

    def test_new_attribute_raise_exception(self):
        self.proxy.new = "NEW"
        self.assertRaises(AttributeError, lambda: self.proxy.new_attr)

class ShadowProxyTestCase(unittest.TestCase):
    def setUp(self):
        unittest.TestCase.setUp(self)
        self.actual = ActualObject()
        self.actual.name = "ACTUAL NAME"
        self.proxy = ShadowProxy(self.actual)

    def test_attributes_pass_thru(self):
        self.assertEqual("ACTUAL NAME", self.proxy.name)

    def test_attributes_are_shadowed(self):
        self.proxy.name = "PROXY NAME"
        self.assertEqual("PROXY NAME", self.proxy.name)

    def test_attributes_are_not_set_on_actual_object(self):
        self.proxy.name = "PROXY NAME"
        self.assertEqual("ACTUAL NAME", self.actual.name)

    def test_unset_attribute_raise_exception(self):
        self.assertRaises(AttributeError, lambda: self.proxy.unset_attr)

    def test_new_attribute_set_proxy_attribute(self):
        self.proxy.new_attr = "NEW"
        self.assertEqual("NEW", self.proxy.new_attr)

    def test_new_attribute_does_not_go_thru(self):
        self.proxy.new_attr = "NEW"
        self.assertRaises(AttributeError, lambda: self.actual.new_attr)

    def test_del_attribute_does_not_go_thru_but_reset(self):
        self.proxy.name = "PROXY NAME"
        del self.proxy.name
        self.assertEqual("ACTUAL NAME", self.proxy.name)


if __name__ == '__main__':
    unittest.main()

test.rb

require "test/unit"
require "read_only_proxy"
require "shadow_proxy"

class ActualObject
  attr_accessor :name
end

class ReadOnlyProxyTest < Test::Unit::TestCase
  def setup
    @actual = ActualObject.new
    @actual.name = "ACTUAL NAME"
    @proxy = ReadOnlyProxy.new(@actual)
  end

  def test_attributes_pass_thru
    assert_equal "ACTUAL NAME", @proxy.name
  end

  def test_attributes_are_not_set_on_actual
    @proxy.name = "PROXY NAME"
    assert_equal "ACTUAL NAME", @actual.name
  end

  def test_attributes_are_not_set_on_proxy
    @proxy.name = "PROXY NAME"
    assert_equal "ACTUAL NAME", @proxy.name
  end

#  def test_unset_attr_raises
#    assert_raise NoMethodError { @proxy.missing_attr }
#  end
end

class ShadowProxyTest < Test::Unit::TestCase
  def setup
    @actual = ActualObject.new
    @actual.name = "ACTUAL NAME"
    @proxy = ShadowProxy.new(@actual)
  end

  def test_attributes_pass_thru
    assert_equal "ACTUAL NAME", @proxy.name
  end

  def test_attributes_are_not_set_on_actual
    @proxy.name = "PROXY NAME"
    assert_equal "ACTUAL NAME", @actual.name
  end

  def test_attributes_are_set_on_proxy
    @proxy.name = "PROXY NAME"
    assert_equal "PROXY NAME", @proxy.name
  end

#  def test_unset_attr_raises
#    assert_raise NoMethodError { @proxy.missing_attr }
#  end
end