####Deinitialization
deinitializer 在对象(对, 这个只有 class 才有)被销毁前调用.is called immediately before a class instance is deallocted. You write deinitializers with the deinitializer keyword, similiar to how initializers are written with the init keyword. Deinitializers are only available on class types.
Class definitions can have at most one deinitializer per class. The deinitializer does not take any parameters and is written without parenthese:
deinit {
// perform the deinitialization
}You are not allowed to call a deinitializer yourself. A deinitializer can access all properties of the instance it is called on and can modify its behavior based on those properties.