气象图标设计，用于气象行业开发，只需动动鼠标就可以了，不过对于批量数据处理以及自动运行的需求无能为力(weather After the execution of an expression, a value will be returned. There are three different kinds of expressions:)

观察者模式，实现数据更新的监听，当有一方面数据变化时，会通知到所有观察者。(The observer pattern, the monitoring of data updates, will notify all observers when there is one aspect of the change in the data.)