摘要：
//Use enum to create an enumeration. Like classes and all other named types, enumerations can have methods associated with them.// swift 中enum 变化比较大，枚... 阅读全文
摘要：
// 下面是苹果给出的解释，就是在给属性设置新值的时候，可以在设置前和设置后做一些处理，这两个关键字就好像对该属性变化的监控If you don’t need to compute the property but still need to provide code that is run bef... 阅读全文