Can I serialise a NSManagedObject?

Question

I need to send an object (NSManagedObject (NSMO) subclass) up to a web service and retrieve it later. I was hoping I could somehow serialise it, but I'm hoping not to have to jump through the encoding hoops.

I can convert a simple NSMO object into a dictionary using: [instance dictionaryWithValuesForKeys:instance.entity.attributesByName.allKeys];

However, my NSMO is a number of levels deep in terms of relationships to other NSMOs. What would be the best way to create a full serialised version of the object?

Answer 1

If you want to do this in a general way, you could write a recursive method serializedDictionary (either in a subclass of NSManagedObject or in a category) which:

1. Creates an empty NSMutableDictionary.
2. For each property , adds the key and value to the dictionary.
3. For each relationship , adds the relationship name as key and then calls serializedDictionary on the object and adds that as the value. If it's a to-many relationship, you'll have to put those values in an NSArray.

Note that if it's at all possible for a child object to be related back up to a parent (which is very possible if you have inverse relationships like Core Data recommends) you will either need to whitelist the relationships you save (easier) or pass along a set to keep track of which objects have already been serialized, so you don't encode them again (harder, I don't recommend this).