Saving an NSMutableArray to Core Data

Question

I want to add an NSMutableArray of NSStrings to one of my Entities in my core data model. The problem is that this isn't a supported type in Core Data.

I tried making a tranformable attribute, but the problem is that I see no way of turning a NSMutableArray to NSData, and then going from NSData, back to an NSMutableArray. Does anyone have an idea as to how this issue can be solved?

(I know I can archive the array, but I don't want to do that, I want it to be present in my model).

Answer 1

You could have a binary data attribute in your modeled object, archive the array to data, and hand it off to the object.

But I think the better way would be to have a to-many relationship, instead of using an array directly.

*Edit: Here's how to archive the array into NSData so that it can be used in your managed object

NSData *arrayData = [NSKeyedArchiver archiveDataWithRootObject:yourStringsArray];

Basically, any class you have which conforms to the NSCoding protocol can be archived in this way. NSArray/NSMutableArray already conform to it. They tell all of their objects to archive themselves, so they must conform too. And all of those objects' members must conform, etc. It's like a tree.

Since your array conforms, and it's an array of NSString (which also conforms), then you're golden.