View Model app restoration setup

ViewController.swift

class ViewController : UIViewController {
    override func decodeRestorableState(with coder: NSCoder) {
        super.decodeRestorableState(with: coder)
        // force class initialization for the sake of state restoration
        ViewModel.classInit
        viewModel = coder.decodeObject(of: ViewModel.self, forKey: "viewModel")
    }
}

ViewModel.swift

@objc(ViewModel)
class ViewModel : NSObject,NSCoding {
    static let classInit : () = {
        // force global initialization for state restoration purposes
        Entry.classInit
    }()
    
    @objc(ViewModel_Entry)
    class Entry : NSObject,NSCoding {
        static let classInit : () = {
            // force global initialization for state restoration purposes
            _ = Entry.self
        }()
    }
}