what is the use with the transfarmable in the xcdatamodal extension

hi开发者_如何学C all just now i started database work for my app.my idea is to save some rectangles(x,y,width,hight individually)as int32 and nsstring as string upto that my work completed .Now my question here is, what is the use with the "transfarmable" type where we can use this. Thanks in advance for your answer.

I'm not sure about transfarmable, but Transformable is:

The idea behind transformable attributes is that you access an attribute as a non-standard type, but behind the scenes Core Data uses an instance of NSValueTransformer to convert the attribute to and from an instance of NSData. Core Data then stores the data instance to the persistent store.

By default, Core Data uses the NSKeyedUnarchiveFromDataTransformerName transformer, however you can specify your own transformer if you want. If you specify a custom transformer, it must transform an instance of the non-standard data type into an instance of NSData and support reverse transformation. You should not specify a name if you are using the default transformer.

as taken from http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CoreData/Articles/cdNSAttributes.html.

Essentially, if you want a custom construct to be serialized into the database and then reconstituted as your desired object/object graph, the Transformable type lets you access Core Data's framework for storing complex formats/objects in the database, letting you code the logic that does the serialization and deserialization.