Current progress

koans/about_classes.rb

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+require File.expand_path(File.dirname(__FILE__) + '/neo')
+
+class AboutClasses < Neo::Koan
+  class Dog
+  end
+
+  def test_instances_of_classes_can_be_created_with_new
+    fido = Dog.new
+    assert_equal __, fido.class
+  end
+
+  # ------------------------------------------------------------------
+
+  class Dog2
+    def set_name(a_name)
+      @name = a_name
+    end
+  end
+
+  def test_instance_variables_can_be_set_by_assigning_to_them
+    fido = Dog2.new
+    assert_equal __, fido.instance_variables
+
+    fido.set_name("Fido")
+    assert_equal __, fido.instance_variables
+  end
+
+  def test_instance_variables_cannot_be_accessed_outside_the_class
+    fido = Dog2.new
+    fido.set_name("Fido")
+
+    assert_raise(___) do
+      fido.name
+    end
+
+    assert_raise(___) do
+      eval "fido.@name"
+      # NOTE: Using eval because the above line is a syntax error.
+    end
+  end
+
+  def test_you_can_politely_ask_for_instance_variable_values
+    fido = Dog2.new
+    fido.set_name("Fido")
+
+    assert_equal __, fido.instance_variable_get("@name")
+  end
+
+  def test_you_can_rip_the_value_out_using_instance_eval
+    fido = Dog2.new
+    fido.set_name("Fido")
+
+    assert_equal __, fido.instance_eval("@name")  # string version
+    assert_equal __, fido.instance_eval { @name } # block version
+  end
+
+  # ------------------------------------------------------------------
+
+  class Dog3
+    def set_name(a_name)
+      @name = a_name
+    end
+    def name
+      @name
+    end
+  end
+
+  def test_you_can_create_accessor_methods_to_return_instance_variables
+    fido = Dog3.new
+    fido.set_name("Fido")
+
+    assert_equal __, fido.name
+  end
+
+  # ------------------------------------------------------------------
+
+  class Dog4
+    attr_reader :name
+
+    def set_name(a_name)
+      @name = a_name
+    end
+  end
+
+
+  def test_attr_reader_will_automatically_define_an_accessor
+    fido = Dog4.new
+    fido.set_name("Fido")
+
+    assert_equal __, fido.name
+  end
+
+  # ------------------------------------------------------------------
+
+  class Dog5
+    attr_accessor :name
+  end
+
+
+  def test_attr_accessor_will_automatically_define_both_read_and_write_accessors
+    fido = Dog5.new
+
+    fido.name = "Fido"
+    assert_equal __, fido.name
+  end
+
+  # ------------------------------------------------------------------
+
+  class Dog6
+    attr_reader :name
+    def initialize(initial_name)
+      @name = initial_name
+    end
+  end
+
+  def test_initialize_provides_initial_values_for_instance_variables
+    fido = Dog6.new("Fido")
+    assert_equal __, fido.name
+  end
+
+  def test_args_to_new_must_match_initialize
+    assert_raise(___) do
+      Dog6.new
+    end
+    # THINK ABOUT IT:
+    # Why is this so?
+  end
+
+  def test_different_objects_have_different_instance_variables
+    fido = Dog6.new("Fido")
+    rover = Dog6.new("Rover")
+
+    assert_equal __, rover.name != fido.name
+  end
+
+  # ------------------------------------------------------------------
+
+  class Dog7
+    attr_reader :name
+
+    def initialize(initial_name)
+      @name = initial_name
+    end
+
+    def get_self
+      self
+    end
+
+    def to_s
+      @name
+    end
+
+    def inspect
+      "<Dog named '#{name}'>"
+    end
+  end
+
+  def test_inside_a_method_self_refers_to_the_containing_object
+    fido = Dog7.new("Fido")
+
+    fidos_self = fido.get_self
+    assert_equal __, fidos_self
+  end
+
+  def test_to_s_provides_a_string_version_of_the_object
+    fido = Dog7.new("Fido")
+    assert_equal __, fido.to_s
+  end
+
+  def test_to_s_is_used_in_string_interpolation
+    fido = Dog7.new("Fido")
+    assert_equal __, "My dog is #{fido}"
+  end
+
+  def test_inspect_provides_a_more_complete_string_version
+    fido = Dog7.new("Fido")
+    assert_equal __, fido.inspect
+  end
+
+  def test_all_objects_support_to_s_and_inspect
+    array = [1,2,3]
+
+    assert_equal __, array.to_s
+    assert_equal __, array.inspect
+
+    assert_equal __, "STRING".to_s
+    assert_equal __, "STRING".inspect
+  end
+
+end