Ruby Hooks: Verify that undef m is same as undefine_method :m

Ruby_Hooks/slides.html

@@ -508,11 +508,13 @@
     * This is how you define a class method --- it's a singleton method on the class itself
 * You will probably find few good reasons to call `remove_method` or `undef_method`
     * See https://ruby-doc.org/core-2.3.0/Module.html#method-i-undef_method for docs
+    * You can also call `undef method_name` instead of `undef_method :method_name`
 * Removing a method will allow any superclass methods to still be called
     * Only example I can think of is if you dynamically added it
 * Undefining a method will set the method to return a `NoMethodError`
     * Only example I can think of is if you're trying to look like an older Ruby
 
+
 ---
 class: strict_conversion
 

Ruby_Hooks/slides.md

@@ -373,11 +373,13 @@ A subclassed in B
     * This is how you define a class method --- it's a singleton method on the class itself
 * You will probably find few good reasons to call `remove_method` or `undef_method`
     * See https://ruby-doc.org/core-2.3.0/Module.html#method-i-undef_method for docs
+    * You can also call `undef method_name` instead of `undef_method :method_name`
 * Removing a method will allow any superclass methods to still be called
     * Only example I can think of is if you dynamically added it
 * Undefining a method will set the method to return a `NoMethodError`
     * Only example I can think of is if you're trying to look like an older Ruby
 
+
 ---
 class: strict_conversion
 

Ruby_Hooks/undef.rb

@@ -0,0 +1,21 @@
+class A
+  def a
+    1
+  end
+end
+
+class B < A
+  def a
+    2
+  end
+end
+
+puts B.new.a
+# => 2
+
+class B
+  undef a
+end
+
+puts B.new.a
+