adding koans from: Metaprogramming in Ruby: It’s All About the Self (h…

…ttp://yehudakatz.com/2009/11/15/metaprogramming-in-ruby-its-all-about-the-self/)

koans/about_self.rb

@@ -0,0 +1,124 @@
+require File.expand_path(File.dirname(__FILE__) + '/edgecase')
+
+# Based on Yehuda Katz's article: Metaprogramming in Ruby: It's all about the self
+# http://yehudakatz.com/2009/11/15/metaprogramming-in-ruby-its-all-about-the-self/
+
+class AboutSelf < EdgeCase::Koan
+
+  class Person
+    def self.species
+      "Homo Sapiens"
+    end
+  end
+
+  def test_self_inside_class_defines_class_method
+    assert_equal __, Person.species
+  end
+
+  @@self_inside_class = class Person
+    self
+  end
+
+  def test_self_inside_class_is_the_class_itself
+    assert_equal __, @@self_inside_class
+  end
+
+  class Dog ; end
+
+  class << Dog
+    def species
+      "Canis Lupus"
+    end
+  end
+
+  def test_self_inside_class_ltlt_class_is_the_metaclass
+    assert_equal __, Dog.species
+  end
+
+  class Cat
+    class << self
+      def species
+        "Felis Catus"
+      end
+    end
+  end
+
+  def test_self_inside_class_ltlt_self_is_the_metaclass
+    # inside class self = Cat
+    # class << self is same as class << Cat
+    assert_equal __, Cat.species
+  end
+
+  class Lion ; end
+
+  @@object = Lion.new
+  @@self_inside_instance_eval_of_object = @@object.instance_eval { self }
+
+  def test_self_inside_instance_eval_of_object_is_the_object_itself
+    assert_equal __, @@self_inside_instance_eval_of_object
+  end
+
+  @@self_inside_instance_eval_of_class = Lion.instance_eval { self }
+
+  def test_self_inside_instance_eval_of_class_is_the_class_itself
+    assert_equal __, @@self_inside_instance_eval_of_class
+  end
+
+  Lion.instance_eval do
+    def species
+      "Panthera Leo"
+    end
+  end
+
+  def test_self_inside_instance_eval_is_class_and_defines_class_methods
+    assert_equal __, Lion.species
+  end
+
+  class Tiger ; end
+
+  def Tiger.species
+    "Panthera Tigris"
+  end
+
+  def test_singleton_method_on_Class_defines_a_class_method
+    assert_equal __, Tiger.species
+  end
+
+  class Person
+    def name
+      "Matz"
+    end
+  end
+
+  def test_methods_defined_in_a_class_are_instance_methods
+    assert_equal __, Person.new.name
+  end
+
+  @@self_inside_class_eval = Cat.class_eval { self }
+
+  def test_self_inside_class_eval_is_the_class_itself
+    assert_equal __, @@self_inside_class_eval
+  end
+
+  Cat.class_eval do
+    def name
+      "Frisky"
+    end
+  end
+
+  def test_class_eval_defines_methods_in_class
+    assert_equal __, Cat.new.name
+  end
+
+  class ::Class
+    def loud_name
+      "#{name.upcase}"
+    end
+  end
+
+  def test_methods_defined_in_Class_class_is_available_to_all_classes
+    # All classes are subclasses of Class and inherit methods of Class
+    assert_match __, Person.loud_name
+  end
+
+end

koans/about_singleton_methods.rb

@@ -12,7 +12,7 @@ def test_instance_method_calls_method_on_parent_class_if_not_found_in_class
     assert_equal __, animal.frozen?
   end
 
-  def test_singleton_method_calls_method_on_anonymous_or_ghost_or_eigen_class
+  def test_singleton_method_calls_method_on_anonymous_or_ghost_or_eigen_or_meta_class
     animal = "cat"
     def animal.speak
       "miaow"

koans/path_to_enlightenment.rb

@@ -3,6 +3,7 @@
 $LOAD_PATH << File.dirname(__FILE__)
 
 require 'about_metaclass'
+require 'about_self'
 require 'about_singleton_methods'
 require 'about_class_as_constant'
 require 'about_class_methods'
@@ -14,4 +15,4 @@
 require 'about_define_method'
 require 'about_instance_eval_and_class_eval'
 require 'about_hook_methods'
-require 'about_method_added'
+require 'about_method_added'

src/about_self.rb

@@ -0,0 +1,124 @@
+require File.expand_path(File.dirname(__FILE__) + '/edgecase')
+
+# Based on Yehuda Katz's article: Metaprogramming in Ruby: It's all about the self
+# http://yehudakatz.com/2009/11/15/metaprogramming-in-ruby-its-all-about-the-self/
+
+class AboutSelf < EdgeCase::Koan
+
+  class Person
+    def self.species
+      "Homo Sapiens"
+    end
+  end
+
+  def test_self_inside_class_defines_class_method
+    assert_equal "Homo Sapiens", Person.species
+  end
+
+  @@self_inside_class = class Person
+    self
+  end
+
+  def test_self_inside_class_is_the_class_itself
+    assert_equal Person, @@self_inside_class
+  end
+
+  class Dog ; end
+
+  class << Dog
+    def species
+      "Canis Lupus"
+    end
+  end
+
+  def test_self_inside_class_ltlt_class_is_the_metaclass
+    assert_equal "Canis Lupus", Dog.species
+  end
+
+  class Cat
+    class << self
+      def species
+        "Felis Catus"
+      end
+    end
+  end
+
+  def test_self_inside_class_ltlt_self_is_the_metaclass
+    # inside class self = Cat
+    # class << self is same as class << Cat
+    assert_equal "Felis Catus", Cat.species
+  end
+
+  class Lion ; end
+
+  @@object = Lion.new
+  @@self_inside_instance_eval_of_object = @@object.instance_eval { self }
+
+  def test_self_inside_instance_eval_of_object_is_the_object_itself
+    assert_equal @@object, @@self_inside_instance_eval_of_object
+  end
+
+  @@self_inside_instance_eval_of_class = Lion.instance_eval { self }
+
+  def test_self_inside_instance_eval_of_class_is_the_class_itself
+    assert_equal Lion, @@self_inside_instance_eval_of_class
+  end
+
+  Lion.instance_eval do
+    def species
+      "Panthera Leo"
+    end
+  end
+
+  def test_self_inside_instance_eval_is_class_and_defines_class_methods
+    assert_equal "Panthera Leo", Lion.species
+  end
+
+  class Tiger ; end
+
+  def Tiger.species
+    "Panthera Tigris"
+  end
+
+  def test_singleton_method_on_Class_defines_a_class_method
+    assert_equal "Panthera Tigris", Tiger.species
+  end
+
+  class Person
+    def name
+      "Matz"
+    end
+  end
+
+  def test_methods_defined_in_a_class_are_instance_methods
+    assert_equal "Matz", Person.new.name
+  end
+
+  @@self_inside_class_eval = Cat.class_eval { self }
+
+  def test_self_inside_class_eval_is_the_class_itself
+    assert_equal Cat, @@self_inside_class_eval
+  end
+
+  Cat.class_eval do
+    def name
+      "Frisky"
+    end
+  end
+
+  def test_class_eval_defines_methods_in_class
+    assert_equal "Frisky", Cat.new.name
+  end
+
+  class ::Class
+    def loud_name
+      "#{name.upcase}"
+    end
+  end
+
+  def test_methods_defined_in_Class_class_is_available_to_all_classes
+    # All classes are subclasses of Class and inherit methods of Class
+    assert_match "PERSON", Person.loud_name
+  end
+
+end

src/path_to_enlightenment.rb

@@ -3,6 +3,7 @@
 $LOAD_PATH << File.dirname(__FILE__)
 
 require 'about_metaclass'
+require 'about_self'
 require 'about_singleton_methods'
 require 'about_class_as_constant'
 require 'about_class_methods'
@@ -14,4 +15,4 @@
 require 'about_define_method'
 require 'about_instance_eval_and_class_eval'
 require 'about_hook_methods'
-require 'about_method_added'
+require 'about_method_added'