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?
Looking at your code, the issue lies within the following function:
func worldMapFilePath(_ fileName: String) -> String {}
This function works fine when you save the World Map, but when you try to retrieve it, the file is getting deleted.
If you log the actual error:
fatalError("Error = \(error)")
rather than using this:
fatalError("Can't get data at url:\(url)")
You will get the following error message:
"The file “WorldMap_test” couldn’t be opened because there is no such file.
Which is more informative than the one provided in your question e.g:
Can't get data at url:file:///var/mobile/Containers/Data/Application/924B012B-B149-4BA7-BFC2-BB79849D866F/Documents/WorldMaps/WorldMap_test
As such some simple changes will solve your issue.
Firstly I recommend moving your call to the createWorldMapsFolder() to viewDidLoad.
Secondly change your func worldMapFilePath(_ fileName: String) -> String {} like so:
func worldMapFilePath(_ fileName: String) -> String {
let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
let documentsDirectory = paths[0] as String
let filePath: String = "\(documentsDirectory)/WorldMaps/WorldMap_\(fileName)"
return filePath
}
Then move your fileExists call to your saveWorldMap function e.g:
func saveWorldMap() {
sceneView.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 worldMapPath = self.worldMapFilePath("test")
if FileManager().fileExists(atPath: worldMapPath) { try! FileManager().removeItem(atPath: worldMapPath) }
let url: URL = URL(fileURLWithPath: worldMapPath)
try data.write(to: url)
} catch {
fatalError("Can't write to url")
}
} catch {
fatalError("Can't encode map")
}
}
}
Hope it helps...