1 “one rule，one place”
2 “design by contract”不用太专业，不用太详细，大白话也行，能让我这个菜鸟看懂就行！ 谢谢了！
1 “one rule，one place”
2 “design by contract”不用太专业，不用太详细，大白话也行，能让我这个菜鸟看懂就行！ 谢谢了！
1 “one rule，one place”
2 “design by contract”不用太专业，不用太详细，大白话也行，能让我这个菜鸟看懂就行！ 谢谢了！
1 “one rule，one place”
2 “design by contract”不用太专业，不用太详细，大白话也行，能让我这个菜鸟看懂就行！ 谢谢了！
A very important implementation strategy to follow is to have only one place where you implement a rule. In other words, if you have a rule how to do things, only implement that once. This typically results in code with a greater number of smaller methods. The extra cost is minimal, but it eliminates duplication and often prevents many future problems. Duplication is bad not only because of the extra work in typing things multiple times, but because of the likelihood of something changing in the future and then forgetting to change it in all of the required places.Although the draw method or Rectangle could directly call the drawLine method of whatever Drawing object the Shape has, I can improve the code by continuing to follow the one rule, one place strategy and have a drawLine method in Shape that calls the drawLine method of its Drawing object.I am not a purist (at least not in most things), but if there is one place where I think it is important to always follow a rule, it is here. In the following example, I have a drawLine method in Shape because that describes my rule of drawing a line with Drawing. I do the same with drawCircle for circles. By following this strategy, I prepare myself for other derived objects that might need to draw lines and circles.