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).