macOS Document Based Application Save&Load

I set up a document based macOS application.
In a custom view (bezierview.swift) I have four NSPoints that I want to Save&Load (in document.swift). As I’m rather unexperienced with Swift3 I have the problem how to get these 4 NSPoints (changed by mouse dragging) from bezierview.swift to document.swift and how to save&load them as e.g. JSON…
Maybe somebody can help.