最病 A Duck Example 9 a Start with a bunch of quackables o a goose came along and wanted to act like a Quakable too Adapter n Then the Quackologists decided they wanted to count lacks. Decorator Abstract factory j o but the quackologists were worried theyd forget to add the Quack Counter decorator a We had management problems keeping track of all those ducks and geese and quackables Composite Iterator n The Qvackologists also wanted to be notified when any quackable quacked. Observer Institute of Computer Software 2021/2/7 Nanjing UniversityDuck Example  Start with a bunch of Quackables..  A goose came along and wanted to act like a Quakable too.  Then, the Quackologists decided they wanted to count quacks.  But the Quackologists were worried they’d forget to add the QuackCounter decorator.  We had management problems keeping track of all those ducks and geese and quackables.  The Quackologists also wanted to be notified when any quackable quacked. 2021/2/7 Institute of Computer Software Nanjing University 9 Adapter Decorator Abstract factory Composite Iterator Observer