Added src directory

src/about_class_methods.rb

@@ -0,0 +1,167 @@
+require 'edgecase'
+
+class AboutClassMethods < EdgeCase::Koan
+  class Dog
+  end
+
+  def test_objects_are_objects
+    fido = Dog.new
+    assert_equal __(true), fido.is_a?(Object)
+  end
+
+  def test_classes_are_classes
+    assert_equal __(true), Dog.is_a?(Class)
+  end
+
+  def test_classes_are_objects_too
+    assert_equal __(true), Dog.is_a?(Object)
+  end
+
+  def test_objects_have_methods
+    fido = Dog.new
+    assert_equal __(45), fido.methods.size
+  end
+
+  def test_classes_have_methods
+    assert_equal __(80), Dog.methods.size
+  end
+
+  def test_you_can_define_methods_on_individual_objects
+    fido = Dog.new
+    def fido.wag
+      :fidos_wag
+    end
+    assert_equal __(:fidos_wag), fido.wag
+  end
+
+  def test_other_objects_are_unaffected_by_these_singleton_methods
+    fido = Dog.new
+    rover = Dog.new
+
+    assert_raise(___(NoMethodError)) do
+      rover.wag
+    end
+  end
+
+  # ------------------------------------------------------------------
+  
+  def Dog.bark
+    :class_level_bark
+  end
+
+  class Dog
+    def bark
+      :instance_level_bark
+    end
+  end
+
+  def test_since_classes_are_objects_you_can_define_singleton_methods_on_them_too
+    assert_equal __(:class_level_bark), Dog.bark
+  end
+
+  def test_class_methods_are_independent_of_instance_methods
+    fido = Dog.new
+    assert_equal __(:instance_level_bark), fido.bark
+    assert_equal __(:class_level_bark), Dog.bark
+  end
+
+  # ------------------------------------------------------------------
+
+  class Dog
+    attr_accessor :name
+  end
+
+  def Dog.name
+    @name
+  end
+
+  def test_classes_and_instances_do_not_share_instance_variables
+    fido = Dog.new
+    fido.name = "Fido"
+    assert_equal __("Fido"), fido.name
+    assert_equal __(nil), Dog.name
+  end
+
+  # ------------------------------------------------------------------
+
+  class Dog
+    def Dog.a_class_method
+      :dogs_class_method
+    end
+  end
+
+  def test_you_can_define_class_methods_inside_the_class
+    assert_equal __(:dogs_class_method), Dog.a_class_method
+  end
+      
+
+  # ------------------------------------------------------------------
+
+  LastExpressionInClassStatement = class Dog
+                                     21
+                                   end
+  
+  def test_class_statements_return_the_value_of_their_last_expression
+    assert_equal __(21), LastExpressionInClassStatement
+  end
+
+  # ------------------------------------------------------------------
+
+  SelfInsideOfClassStatement = class Dog
+                                 self
+                               end
+
+  def test_self_while_inside_class_is_class_object_not_instance
+    assert_equal __(true), Dog == SelfInsideOfClassStatement
+  end
+
+  # ------------------------------------------------------------------
+
+  class Dog
+    def self.class_method2
+      :another_way_to_write_class_methods
+    end
+  end
+
+  def test_you_can_use_self_instead_of_an_explicit_reference_to_dog
+    assert_equal __(:another_way_to_write_class_methods), Dog.class_method2
+  end
+
+  # ------------------------------------------------------------------
+
+  class Dog
+    class << self
+      def another_class_method
+        :still_another_way
+      end
+    end
+  end
+
+  def test_heres_still_another_way_to_write_class_methods
+    assert_equal __(:still_another_way), Dog.another_class_method
+  end
+
+  # THINK ABOUT IT:
+  #
+  # The two major ways to write class methods are:
+  #   class Demo
+  #     def self.method
+  #     end
+  #
+  #     class << self
+  #       def class_methods
+  #       end
+  #     end
+  #   end
+  #
+  # Which do you prefer and why?
+  # Are there times you might prefer the other way?
+
+  # ------------------------------------------------------------------
+
+  def test_heres_an_easy_way_to_call_class_methods_from_instance_methods
+    fido = Dog.new
+    assert_equal __(:still_another_way), fido.class.another_class_method
+  end
+
+end