Add to arrayController, edit Core Data attribute

Answer 1

NSArray's add: method is something you'd hook a button up to, when you have a Core Data entity that can be created and used without any initialization. In this case just call NSEntityDescription's

+ (id)insertNewObjectForEntityForName:(NSString *)entityName inManagedObjectContext:(NSManagedObjectContext *)context

with the managed object context you're using with your array controller and the appropriate entity name to create your managed object in code. You can set properties on it directly if you've created a subclass for your entity, or just use key value coding if you haven't done that yet.