0.3.1 Introduction

• Don’t understand Design pattern by language. Such as factory method and template method, They share the same language structure( class inheritance and structure). But their context is different.
• Easy pattern: singleton, Facade, adapter, mediator, observe, Prototype, strategy, factory method, template mehod, command, proxy, memento.
• Three use recursive: composite, decorator, chain of responsibility and Interpreter.
• Bridge , abstractor factory and visitor have same points, they all have parallel two inheritance system, there is a relationship between two systems.
• Template method and Factory method are both pull up common and push down change. Template pull up common algorithm steps and Create templateMethod(). And Factory method pull up common produced procession and Create factoryMethod.
• Sometimes, You want to pull up common. But there is NO concrete conception(A noun) waiting here, then you can abstract a conception, and make an abstract class as base class.
  1. Button and applicaition should not have baseclass, but they both support requestHandle(), So you create Handler class.
  2. Textview and decorator should not have base class, but after decoration, textview is still textview. So I create VisualComponent Base class.
  3. In Mediator pattern. Listbox and EntryField have now common baseclass, So create Colleague baseclass.
  4. Proxy is also follow this idea.

  

• Program to interface. But where are interfaces?
  1. You can pull up to create baseclass interface: such as component, chain of responsible, decorator and proxy.
  2. You can create a medium class(interface) . such as command between invoker and Receiver, Memento between Originator and caretaker. adapter between Target and Adaptee. Mediator between Colleague and ConcreteMediator.
  3. Iterator between container and algorithms. builder between Director and product.