about_scope.rb

require File.expand_path(File.dirname(__FILE__) + '/edgecase')

class AboutScope < EdgeCase::Koan
  module Jims
    class Dog
      def identify
        :jims_dog
      end
    end
  end

  module Joes
    class Dog
      def identify
        :joes_dog
      end
    end
  end

  def test_dog_is_not_available_in_the_current_scope
    assert_raise(NameError) do
      fido = Dog.new
    end
  end

  def test_you_can_reference_nested_classes_using_the_scope_operator
    fido = Jims::Dog.new
    rover = Joes::Dog.new
    assert_equal :jims_dog, fido.identify
    assert_equal :joes_dog, rover.identify

    assert_equal true, fido.class != rover.class
    assert_equal true, Jims::Dog != Joes::Dog
  end

  # ------------------------------------------------------------------

  class String
  end

  def test_bare_bones_class_names_assume_the_current_scope
    assert_equal true, AboutScope::String == String
  end

  # Not a match because the String reference here matches the String 
  # class within this class (AboutScope). That's the default behavior. 
  # Whereas the string "HI" will use the language defined String class.
  def test_nested_string_is_not_the_same_as_the_system_string
    # puts String     # > AboutScope::String
    # puts "HI".class # > String
    assert_equal false, String == "HI".class
  end

  # Since if we use String it would reference the String class within 
  # this class, to always make sure we get the global system defined 
  # one we just prefix it with ::
  def test_use_the_prefix_scope_operator_to_force_the_global_scope
    # puts ::String   # > String
    # puts "HI".class # > String
    assert_equal true, ::String == "HI".class
  end

  # ------------------------------------------------------------------

  PI = 3.1416

  def test_constants_are_defined_with_an_initial_uppercase_letter
    assert_equal 3.1416, PI
  end

  # ------------------------------------------------------------------
  
  # Class names are just constants. Remember in Ruby just the first 
  # letter of a variable if capitalized makes it a constant.
  # http://www.ruby-doc.org/docs/ProgrammingRuby/html/classes.html
  # You can pass around Classes just like you can in AS3, for example, 
  # we can pass a Class like String to a method and reference a method 
  # on that argument.
  # 
  # def factory(klass, *args)
  #   klass.new(*args)
  # end
  # factory(String, "Hello"  # > "Hello"
  
  MyString = ::String

  def test_class_names_are_just_constants
    assert_equal true, MyString == ::String
    assert_equal true, MyString == "HI".class
  end

  def test_constants_can_be_looked_up_explicitly
    assert_equal true, PI == AboutScope.const_get("PI")
    assert_equal true, MyString == AboutScope.const_get("MyString")
  end

  def test_you_can_get_a_list_of_constants_for_any_class_or_module
    assert_equal ["Dog"], Jims.constants
    assert Object.constants.size > 0
  end
end