moving to a new repo

about_message_passing.rb

@@ -0,0 +1,167 @@
+require 'edgecase'
+
+class AboutMessagePassing < EdgeCase::Koan
+  
+  class MessageCatcher
+    def caught?
+      true
+    end
+  end
+    
+  def test_methods_can_be_called_directly
+    mc = MessageCatcher.new
+    
+    assert mc.caught?    
+  end
+  
+  def test_methods_can_be_invoked_by_sending_the_message
+    mc = MessageCatcher.new
+    
+    assert mc.send(:caught?)
+  end
+  
+  def test_methods_can_be_invoked_more_dynamically
+    mc = MessageCatcher.new
+    
+    assert mc.send("caught?")
+    assert mc.send("caught" + __ )    # What do you need to add to the first string?
+    assert mc.send("CAUGHT?".__ )      # What would you need to do to the string?
+  end
+
+  def test_send_with_underscores_will_also_send_messages
+    mc = MessageCatcher.new
+
+    assert_equal __, mc.__send__(:caught?)
+
+    # THINK ABOUT IT:
+    #
+    # Why does Ruby provide both send and __send__ ?
+  end
+
+  def test_classes_can_be_asked_if_they_know_how_to_respond
+    mc = MessageCatcher.new
+    
+    assert_equal __, mc.respond_to?(:caught?)
+    assert_equal __, mc.respond_to?(:does_not_exist)
+  end
+  
+  # ------------------------------------------------------------------
+
+  class MessageCatcher
+    def add_a_payload(*args)
+      return :empty unless args
+      args
+    end
+  end
+  
+  def test_sending_a_message_with_arguments
+    mc = MessageCatcher.new
+    
+    assert_equal __, mc.add_a_payload
+    assert_equal __, mc.send(:add_a_payload)
+
+    assert_equal __, mc.add_a_payload(3, 4, nil, 6)
+    assert_equal __, mc.send(:add_a_payload, 3, 4, nil, 6)
+  end
+
+  # ------------------------------------------------------------------
+
+  class TypicalObject
+  end
+
+  def test_sending_undefined_messages_to_a_typical_object_results_in_errors
+    typical = TypicalObject.new
+
+    assert_raise(___) do
+      typical.foobar
+    end
+    assert_match(/foobar/, exception.message)
+  end
+
+  def test_calling_method_missing_causes_the_no_method_error
+    typical = TypicalObject.new
+
+    exception = assert_raise(___) do
+      typical.method_missing(:foobar)
+    end
+    assert_match(/foobar/, exception.message)
+
+    # THINK ABOUT IT:
+    #
+    # If the method :method_missing causes the NoMethodError, then
+    # what would happen if we redefine method_missing?
+  end
+
+  # ------------------------------------------------------------------
+
+  class AllMessageCatcher
+    def method_missing(method_name, *args, &block)
+      "Someone called #{method_name} with (#{args.join(", ")})"
+    end
+  end
+
+  def test_all_messages_are_caught
+    catcher = AllMessageCatcher.new
+
+    assert_equal __, catcher.foobar
+    assert_equal __, catcher.foobaz(1)
+    assert_equal __, catcher.sum(1,2,3,4,5,6)
+  end
+
+  def test_catching_messages_makes_respond_to_lie
+    catcher = AllMessageCatcher.new
+
+    assert_nothing_raised(NoMethodError) do
+      catcher.any_method
+    end
+    assert_equal __, catcher.respond_to?(:any_method)
+  end
+
+  # ------------------------------------------------------------------
+
+  class WellBehavedFooCatcher
+    def method_missing(method_name, *args, &block)
+      if method_name.to_s[0,3] == "foo"
+        "Foo to you too"
+      else
+        super(method_name, *args, &block)
+      end
+    end
+  end
+
+  def test_foo_method_are_caught
+    catcher = WellBehavedFooCatcher.new
+
+    assert_equal __, catcher.foo_bar
+    assert_equal __, catcher.foo_baz
+  end
+
+  def test_non_foo_messages_are_treated_normally
+    catcher = WellBehavedFooCatcher.new
+
+    assert_raise(___) do
+      catcher.normal_undefined_method
+    end
+  end
+
+  # ------------------------------------------------------------------
+
+  # (note: just reopening class from above)
+  class WellBehavedFooCatcher
+    def respond_to?(method_name)
+      if method_name.to_s[0,3] == "foo"
+        true
+      else
+        super(method_name)
+      end
+    end
+  end
+
+  def test_explicitly_implementing_respond_to_lets_objects_tell_the_truth
+    catcher = WellBehavedFooCatcher.new
+
+    assert_equal __, catcher.respond_to?(:foo_bar)
+    assert_equal __, catcher.respond_to?(:something_else)
+  end
+
+end