Exercise 42: Is-A, Has-A, Objects, and Classes

ex42.rb

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+# Animal is-a object look at the extra credit
+class Animal
+end
+
+# ??
+class Dog < Animal
+
+  def initialize(name)
+    # ??
+    @name = name
+  end
+end
+
+# ??
+class Cat < Animal
+
+  def initialize(name)
+    # ??
+    @name = name
+  end
+end
+
+# ??
+class Person
+
+  def initialize(name)
+    # ??
+    @name = name
+
+    # Person has-a pet of some kind
+    @pet = nil
+  end
+
+  attr_accessor :pet
+end
+
+# ??
+class Employee < Person
+
+  def initialize(name, salary)
+    # ?? hmm what is this strange magic?
+    super(name)
+    # ??
+    @salary = salary
+  end
+
+end
+
+# ??
+class Fish
+end
+
+# ??
+class Salmon < Fish
+end
+
+# ??
+class Halibut < Fish
+end
+
+
+# rover is-a Dog
+rover = Dog.new("Rover")
+
+# ??
+satan = Cat.new("Satan")
+
+# ??
+mary = Person.new("Mary")
+
+# ??
+mary.pet = satan
+
+# ??
+frank = Employee.new("Frank", 120000)
+
+# ??
+frank.pet = rover
+
+# ??
+flipper = Fish.new()
+
+# ??
+crouse = Salmon.new()
+
+# ??
+harry = Halibut.new()