Using File Archives
In Chapter 7, you learned the basics of reading and writing document data. One common way of doing this is to convert your own data from whatever its structure and format is to an NSData object (now a Data object), which can be read or written with a simple statement. The only catch to this is that you need to do the conversion from your data type to Data. One of the simplest and most used techniques is to use the built-in archiving technology in Cocoa.