ARKit 4.0 – Is it possible to convert ARWorldMap data to JSON file?

Question

I'd like to know whether it is possible to convert a worldMap binary data (that stores a space-mapping state and set of ARAnchors) to json or xml file?

func writeWorldMap(_ worldMap: ARWorldMap, to url: URL) throws {

    let data = try NSKeyedArchiver.archivedData(withRootObject: worldMap, 
                                         requiringSecureCoding: true)
    try data.write(to: url)
}

If this possible, what tools can I use for that?

Answer 1

I am afraid that the only way to do this is by wrapping the ARWorldMap object into a Codable object like that:

struct ARData {
    var worldMap: ARWorldMap?
}

extension ARData: Codable {
    enum CodingKeys: String, CodingKey {
        case worldMap
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)

        let worldMapData = try container.decode(Data.self, forKey: .worldMap)
        worldMap = try NSKeyedUnarchiver.unarchivedObject(ofClass: ARWorldMap.self, from: worldMapData)
    }
    
    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        
        if let worldMap = worldMap {
            let colorData = try NSKeyedArchiver.archivedData(withRootObject: worldMap, requiringSecureCoding: true)
            try container.encode(colorData, forKey: .worldMap)
        }
    }
}

To encode an instance of that object to JSON use the encode(:) function of the JSONEncoder:

let arData = ARData(worldMap: worldMap)
let encoder = JSONEncoder()

do {
    let jsonData = try encoder.encode(arData)
} catch {
    print(error)
}

By default, JSONEncoder will convert the ARWorldMap data to a Base64 string that can be read using JSONDecoder:

let decoder = JSONDecoder()

do {
    let decoded = try decoder.decode(ARData.self, from: jsonData)
} catch {
    print(error)
}