https://medium.com/better-programming/core-data-basics-swift-persistent-storage-ba3185fe7061

Getting StartedCore data is a great option for persistent data in Swift, but some people find the barriers to using it for their apps to be too high. In this piece, we will look at the main components of the Core Data stack, break them down and try to make their use comprehensible for the first time user.

You save on the context rather than on the objects themselves. This makes sense, as this is the environment that holds the ManagedObjects.