您的SKProduct类需要符合NSCoding协议。

Your SKProduct class needs to conform to the NSCoding protocol.

换句话说，您需要在SKProduct类中填写这两个方法。

In other words you need to fill out these two methods in your SKProduct class.

• （void）encodeWithCoder：（NSCoder *）aCoder;


• （id）initWithCoder：（NSCoder *）aDecoder;

这将带你的SKProduct类，并将其分解，以便它可以序列化和反序列化。

This will take your SKProduct class and break it down so that it can be serialized and unserialized.