正如大多数其他模式一样，观察者模式的作用远远超过了其最初的想法。-icensee may receive a full refund if within thirty (30) days from the date of delivery (the "Acceptance Period") Licensee does not accept the terms and conditions of this License and the applicable Addendum,

使用MVC模式和观察者模式实现画圆和计算面积、表面积-Use the MVC pattern and the observer pattern implementation Circle and computing area, surface area

本代码对观察者模式给与举例，适合于用模式开发工程的同学和研究者。-This code gives an example of the observer pattern, suitable for use in the mode of development of students and researchers