Tech in Pieces

It’s a very important principle in OOP.Single responsibility : every single class should just do one thingOpen closed: extension but not modificationLiskov substitution: any instance in any place, we can just replace it with it’s subclass instance witho

首先想一想有哪些类: request elevatorSystem, evalator, elevatorButtons然后画出UML图，当然 这个图我们也不可能一下子就画出来的，要先想一下User case.所谓的user case，就是每个类都需要做什么操作。比如说 elevator:，有如下几个user cases:take external requesttake internal requestopen gateclose gatecheck weight还有一个elevator