Loading Data from file with Data(contentsOf: url)

I'm trying to save then load an ARKit `ARWorldMap` to a local file. I seem to have the saving working fine:


func saveWorldMap() {
       
        ARView?.session.getCurrentWorldMap { [unowned self] worldMap, error in
           
            guard let map = worldMap else { return }
           
            do {
                let data = try NSKeyedArchiver.archivedData(withRootObject: map, requiringSecureCoding: true)
                do {
                    let url: URL = URL(fileURLWithPath: self.worldMapFilePath("test"))
                    try data.write(to: url)
                } catch {
                    fatalError("Can't write to url")
                }
            } catch {
                fatalError("Can't encode map")
            }
        }
       
    }




    func worldMapFilePath(_ fileName: String) -> String {
       
        createWorldMapsFolder()
        let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
        let documentsDirectory = paths[0] as String
        let filePath: String = "\(documentsDirectory)/WorldMaps/WorldMap_\(fileName)"
        if FileManager().fileExists(atPath: filePath) { try! FileManager().removeItem(atPath: filePath) }
        return filePath
       
    }


    func createWorldMapsFolder() {
       
        let documentDirectoryPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first
        if let documentDirectoryPath = documentDirectoryPath {
           
            let replayDirectoryPath = documentDirectoryPath.appending("/WorldMaps")
            let fileManager = FileManager.default
           
            if !fileManager.fileExists(atPath: replayDirectoryPath) {
               
                do {
                    try fileManager.createDirectory(atPath: replayDirectoryPath, withIntermediateDirectories: false, attributes: nil)
                } catch {
                    print("Error creating Captures folder in documents dir: \(error)")
                }
            } else {
                print("WorldMaps folder already created. No need to create.")
            }
        }
       
    }


The problem comes when I try to then load that saved ARWorldMap:



func loadWorldMap() {
       
        guard let data = retrieveWorldMapDataForFilename("test") else { fatalError("Can't get data") }
       
        do {
            let worldMap = try NSKeyedUnarchiver.unarchivedObject(ofClass: ARWorldMap.self, from: data)
            startSession(options: [.resetTracking, .removeExistingAnchors], initialWorldMap: worldMap)
           
        } catch {
            fatalError("Can't get worldMap")
        }       
       
    }
   
    func retrieveWorldMapDataForFilename(_ filename: String) -> Data? {
       
        let url: URL = URL(fileURLWithPath: self.worldMapFilePath(filename))
        do {
            let data = try Data(contentsOf: url)
            return data
        } catch {
            fatalError("Can't get data at url:\(url)")
        }
       
    }


When this I try to load the saved `ARWorldMap` with `loadWorldMap()` the bottom fatalError there in `retrieveWorldMapDataForFilename(_ filename: String)`, is caught with the following error


Thread 1: Fatal error: Can't get data at url:file:///var/mobile/Containers/Data/Application/924B012B-B149-4BA7-BFC2-BB79849D866F/Documents/WorldMaps/WorldMap_test



What am I doing wrong?

Accepted Reply

So, probably, the intent is to have the test


if FileManager().fileExists(atPath: filePath) { try! FileManager().removeItem(atPath: filePath) }


not in worldMapFilePath() but in saveWorldMap() before data.write

Replies

Sorry if I missed it - is that error when simulator testing, or device?

Your worldMapFilePath() function deletes the file if it already exists.

So, probably, the intent is to have the test


if FileManager().fileExists(atPath: filePath) { try! FileManager().removeItem(atPath: filePath) }


not in worldMapFilePath() but in saveWorldMap() before data.write