D. The data storage at client terminal
At iOS client there are two ways to story the dishes data
receiving from the server: one way is to store it temporarily in
memory and will disappear aft er login out, the data can be
stored in an object array; The other way is persistent data
storage at client. There are four different methods in iOS
system: property list(plist),object archive, database
storage(SQLite3),Core Data.