Need a feature or function(s) to save drawing made with Swift for iOS Mobile App

Hi there. I have an app that allows the user to draw on a device with an Apple Pencil or even their finger. I'm looking for a function that will allow me to save and then re-open their drawing and re-render it so they can continue drawing at a later point in time.

I just need the function or functions and I can try them in our app because I can't share the code.

Thanks!