How do I persist a dictionary if the object is an item from a class that stores three values in Swift?

Question

I'm trying to store a mutable (I believe that shouldn't make a difference, as it will be immutable once it's retrieved from NSUserDefaults) dictionary with NSUserDefaults, that has objects from a class which holds two string values and one boolean value, for the objects, but I'm running into an error, with the reason being I'm trying to insert a non-property list object.

Should I look into using Core Data? If not, what should I do? I've looked all over, but can't seem to find anything

I'm just learning Swift and programming in general, so please excuse my lack of knowledge