Core Data not saving transformable NSMutableDictionary

Question

I have two classes: Profile and Config. A Profile contains an NSSet of Config objects. Both Profile and Config are NSManagedObject subclasses.

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Answer 1

You've declared myDict as an NSMutableDictionary which is a big red flag.

Managed object attributes should never be a mutable type

Chances are, you're using myDict something like this:

someConfig.myDict[@"someKey"] = @"someValue";
[context save:&error];

The problem is, you're not calling a setter method of someConfig so you've done nothing to inform it that an attribute has been changed. And even though you're calling save:, the context doesn't bother saving unchanged objects.

Strictly speaking, you could probably get away with calling [someConfig didChangeValueForKey:@"myDict"] every time you change myDict. I wouldn't recommend it though because it's easy to forget and error prone.

It would better to declare myDict as non-mutable and use it like this:

@property (nonatomic, retain) NSDictionary *myDict;
...
NSMutableDictionary *updatedDict = [someConfig.myDict mutableCopy];
updatedDict[@"someKey"] = @"someValue";
someConfig.myDict = [updatedDict copy];
[context save:&error];