Saving/loading files: "warning: dynamic accessors failed to find #property implementation for 'uniqueId'" - swift

Question

I am trying to save/load an object to file, and for this I am just converting the object (self.game) to an array containing dictionaries, and then using write(toFile:atomically:). But the saveGame method doesn't do anything: I am allowed to choose a file, to press OK and the save panel gets dismissed, but the file isn't really saved. When I use the loadGame method I see that a strange error appears:
warning: dynamic accessors failed to find #property implementation for 'uniqueId' for entity ABCDInfo while resolving selector 'uniqueId' on class 'ABCDInfo'. Did you remember to declare it #dynamic or #synthesized in the #implementation ?
#IBAction func saveGame(_ sender: NSButton) {
let savePanel = NSSavePanel()
savePanel.allowedFileTypes = ["com.apple.property-list"]
if savePanel.runModal() == NSFileHandlingPanelOKButton {
let file = savePanel.url!.absoluteString
self.game.write(toFile: file)
}
}
#IBAction func loadGame(_ sender: NSButton) {
let openPanel = NSOpenPanel()
openPanel.allowedFileTypes = ["com.apple.property-list"]
if openPanel.runModal() == NSFileHandlingPanelOKButton {
let file = openPanel.url!.absoluteString
self.game = Game(withFile: file)
self.selectedSlot = nil
self.enemySlot = nil
self.restartButton.isEnabled = false
self.updateTurnLabel()
self.chessboardView.reloadData()
}
}
The self.game.write(toFile:) method just converts the object to a NSArray and writes it to the file passed as argument.

Answer 1

When you save an array with a dictionary, you can simply use writeToFile in Objective-C. But the same is not true for Swift unless the keys are absolutely string objects. You have to first archive it with NSKeyedArchiver. You can then write it to a file. If you don't archive it, you can end up with no file with or without a warning. The following is an example.
let title = recordArray[r1].valueForKey("texttitle") as! String
let text = recordArray[r1].valueForKey("texttext") as! String
let urls = recordArray[r1].valueForKey("urls") as! String
var codeArray = [NSDictionary]()
let dict = ["Title":title,"URLs":urls,"Code":text] as NSDictionary // or Dictionary
codeArray.append(dict)
let data = NSKeyedArchiver.archivedDataWithRootObject(codeArray)
data.writeToFile(path, atomically: true)
When you open a file, use NSKeyedUnarchiver to unarchive data.