(Possible Solution) Documents Made of Nested Types

Using Swift
1

How could one take a data model with nested types (like the one below) and have the data stored in a document? Thanks.

class ContentCell {

var isMarkedOff: Bool = false 
var cellText: String = ""

}



class CellRow {

var RowCells: [ContentCell] = [ContentCell(), ContentCell(), ContentCell()]

}



class FullChart {

var ChartRows: [CellRow] = [CellRow()] 

}
2

I think I may have found a solution, (or rather, realized a had been missing it), but some related code (specified blow) seems to cause an error to be thrown, so I can't test it. The code syntax is straight from an Apple tutorial, so it might be outdated.

import SwiftUI
import UniformTypeIdentifiers
import CoreServices

@main
struct Test_ProjectApp: App {
    var body: some Scene {  
        DocumentGroup(newDocument: Test_ProjectDocument()) { file in
            ContentView(document: file.$document)
        }
    }
}



////

extension UTType {
    static let Test_ProjectDocument =
        UTType(exportedAs: "com.testproject")
}



struct Test_ProjectDocument: FileDocument, Codable { // < Type conformance error is thrown, seemingly because the type checker wants the fileWrapper stuff (bellow) in a different syntax.   

 // The FileDocument struct can have properties defined, and initialized here: // 

    var fullTable: [CellRow] // < Each CellRow instance is saved in this array ("fullTable").  
                             // The type "CellRow" can have properties which are arrays of other types.  

    
    init() {
        self.fullTable = []  // < empty array.  Start items can be defined inside.  
    }

 // 

    static var readableContentTypes: [UTType] { [.Test_ProjectDocument] }


 // These don't seem to work as in the tutorial "Building Document Based Apps With swiftUI - WWDC20" // 
    init(fileWrapper: FileWrapper, contentType: UTType) throws {
        let data = fileWrapper.regularFileContents!
        self = try JSONDecoder().decode(Self.self, from: data)
    }
    
    func write(to fileWrapper: inout FileWrapper, contentType: UTType) throws {
        let data = try JSONEncoder().encode(self)
        fileWrapper = FileWrapper(regularFileWithContents: data)
    }
  //

}


//// Rest of data model ////


Public struct CellRow : Hashable, Codable, Identifiable {
       public var id: Int 

        var CellsOfRow: [ContentCell] = [ContentCell(), ContentCell(), ContentCell()] // < Array could be left empty. 

} 


struct ContentCell {   // < A class probably wouldn't work with fileDocument, from what I've heard.  

var isMarkedOff: Bool = false 
var cellText: String = ""

}

Any help would be greatly appreciated.