Errors with Archiving / Unarchiving NSMutableDictionary - ios

Question

In my application, I have a dictionary called matchDataDictionary and I set the following:
[[GCTurnBasedMatchHelper sharedInstance].matchDataDictionary setObject:deck forKey:#"deck"];
where deck is an instance of Deck: https://gist.github.com/naderhen/4711899
I then am trying to just test the archiving/unarchiving with the following:
Archiving (this seems to work):
NSMutableData *newData = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:newData];
[archiver encodeObject:[GCTurnBasedMatchHelper sharedInstance].matchDataDictionary forKey:#"root"];
[archiver finishEncoding];
NSLog(#"Archived Data: %#", newData);
Unarchiving (Doesn't Work):
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:newData];
NSMutableDictionary *matchDataDictionary = [unarchiver decodeObjectForKey:#"root"];
[unarchiver finishDecoding];
NSLog(#"Unarchived Data: %#", matchDataDictionary);
Any guidance as to how I can go about effectively archiving and subsequently unarchiving this data would be greatly appreciated. If it helps, this is for a turn-based game using the GameKit framework, so I'm trying to prepare user actions to send via the current match's matchData.
Also! Any advice on how I might fix up the Deck encoding to include its "Tiles" array would be greatly appreciated.
Thanks so much!
Nader

Answer 1

Use the NSCoding protocol. Each entity encodes itself, and then decodes itself. Kind of magical how easy it is, and as the app grows, people can add the functionality to the new parts of the object graph without knowing anything about the archivers/unarchivers, or their formats.
NSCoding Protocol
I have an open source project on GitHub that makes it easy to do NSCoding to/from JSON: JSONCoding.
Here is some code from before I developed that (out of a unit test):
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:firstDish];
RestaurantDish *retrievedDish = [NSKeyedUnarchiver unarchiveObjectWithData:data];
assertThat(retrievedDish.name, is(dishName));
The instance firstDish is just an entity Dish that represents a plate of food.