3.4 面向对象分析面向对象设计（初步）

Posted 2021-02-13 mayzhou

一般原则

　　? An object-oriented system is composed of objects sending messages to other objects

　　? The quality of the overall design depends on which object is doing what

　　　　? 比喻：“人尽其责、各有所长”

　　? That is, the quality depends on how we assign responsibilities to the objects

　　? Problem:

　　　　? Define “good quality”？
职责驱动的设计 (RDD)

　　? RDD，Responsibility Driven Design

　　　　? Pioneered by Wirfs-Brock in early 90s

　　　　? Think of objects in terms of what they do or know (the human worker metaphor!)

　　　　　　设计时考虑对象做什么、或者知道什么
　　　　? An object’s obligation or contract that it offers to other objects

　　　　　　一个对象对其他对象承担的义务或者合约

　　　　? A responsibility is really a behavior the other classes depend on

　　　　　　职责是一个对象的行为，而其他的对象依赖这种行为 
职责的定义 Responsibilities

　　? 这里定义为两类Knowing、Doing
　　? 认知职责 Knowing

　　　　? about private encapsulated data

　　　　? about related objects

　　　　? about things it can derive or calculate
　　? 行为职责 Doing

　　　　? doing something itself

　　　　? initiating action in other objects

　　　　? controlling and coordinating activities in other objects