How to save and fetch data from file in swift?

Question

I want to save the response from JSON in a file and fetch from it when the network is not available. However on trying to fetch idea by disabling the wifi, the app always crashes. Are there any other ways for offline fetching in swift except saving in database??

This is the error I am getting : Could not cast value of type 'Swift._NSContiguousString' (0x109e22320) to 'NSArray'

This is what I have done so far:

• Create a model

  class Directory : NSObject, NSCoding {
  
  
      var data : [AnyObject]
      var tid  : String
      var vid  : String
      var name : String
      var imgThumbnail : String
      var imgMedium : String
      var imgLarge : String
      var child : String
  
      // MARK: Archiving Paths
  
      init(data:[AnyObject],tid:String,vid:String,name:String,imgThumbnail:String,imgMedium:String,imgLarge:String,child:String) {
  
          self.data = data ?? []
          self.tid = tid ?? ""
          self.vid = vid ?? ""
          self.name = name ?? ""
          self.imgThumbnail = imgThumbnail ?? ""
          self.imgMedium   = imgMedium ?? ""
  
          self.imgLarge = imgLarge ?? ""
          self.child = child ?? ""
  
      }
      // MARK: NSCoding
  
      func encodeWithCoder(aCoder: NSCoder) {
          aCoder.encodeObject(data, forKey:Constants.kData)
          aCoder.encodeObject(name, forKey:Constants.Directory.kName )
          aCoder.encodeObject(tid, forKey: Constants.Directory.tid)
          aCoder.encodeObject(vid, forKey: Constants.Directory.vid)
          aCoder.encodeObject(imgThumbnail, forKey:Constants.Directory.kImageThumbnail)
          aCoder.encodeObject(imgMedium, forKey: Constants.Directory.kImageMedium)
          aCoder.encodeObject(imgLarge, forKey: Constants.Directory.kImageLarge)
          aCoder.encodeObject(child, forKey: Constants.Directory.kChild)
      }
  
      required convenience init?(coder aDecoder: NSCoder) {
  
          let data = aDecoder.decodeObjectForKey(Constants.kData) as! [AnyObject]
          let name = aDecoder.decodeObjectForKey(Constants.Directory.kName) as! String
  
  
          let tid = aDecoder.decodeObjectForKey(Constants.Directory.tid) as! String
  
          let vid = aDecoder.decodeObjectForKey(Constants.Directory.vid) as! String
          let imgThumbnail = aDecoder.decodeObjectForKey(Constants.Directory.kImageThumbnail) as! String
          let imgMedium = aDecoder.decodeObjectForKey(Constants.Directory.kImageMedium) as! String
          let imgLarge = aDecoder.decodeObjectForKey(Constants.Directory.kImageLarge) as! String
          let child = aDecoder.decodeObjectForKey(Constants.Directory.kChild) as! String
  
  
          // Must call designated initializer.
          self.init(data:data,tid:tid,vid:vid,name:name,imgThumbnail:imgThumbnail,imgMedium: imgMedium,imgLarge: imgLarge, child: child)
      }
  }
  

• Code for saving and loading the data from file

  class func loadSavedFile(fileName: String) -> AnyObject? {
      let pathString: String = Utility.fetchFilePathString(fileName)
      print("Here the pathString is \(pathString)")
      if NSFileManager.defaultManager().fileExistsAtPath(pathString) {
          return NSKeyedUnarchiver.unarchiveObjectWithFile(pathString)!
      } else {
          return "File doesn't exist"
      }
      return ""
  }
  
  class func saveObject(object: AnyObject, toFile fileName: String) {
      let pathString: String = Utility.fetchFilePathString(fileName)
      NSKeyedArchiver.archiveRootObject(object, toFile: pathString)
  }
  
  class func fetchFilePathString(fileName: String) -> String {
      let pathAray: [AnyObject] = NSSearchPathForDirectoriesInDomains(.DocumentDirectory,.AllDomainsMask, true)
      let pathString = pathAray.last!
      return NSURL(fileURLWithPath: pathString as! String).URLByAppendingPathComponent(fileName).absoluteString
  }
  

• Checking for network connection in the view controller

  var directoryArr  = [Directory]()
  override func viewDidLoad() {
  
      super.viewDidLoad()
  
      if Utility.isNetworkReachable() {
          Utility.saveObject([], toFile: Constants.File.kDirectory)
          self.serviceCallDirectory()
      } else {
          self.directorie = (Utility.loadSavedFile(Constants.File.kDirectory) as? [Directory])!
          self.tableView.reloadData()
      }
  

• Service Call

  func serviceCallDirectory() -> Void {
      let stringUrl = Constants.baseUrl + Constants.kDirectoryUrl
      WebService.getRequestAPI(stringUrl, withSuccess:  {(responseDic, Statusflag,error) in
          if Statusflag {
              self.tableView.backgroundColor = UIColor.clearColor()
              self.tableView.hidden = false
  
              let tempInfo = responseDic![Constants.kData] as! [AnyObject]
              var imgthumbnail : String = ""
              var imgmedium : String = ""
              var imglarge : String = ""
              var name  : String = ""
              var child : String = ""
              if tempInfo.count != 0 {
                  for info in tempInfo {
                      let tid = info[Constants.Directory.tid] as! String
                      let vid = info[Constants.Directory.vid] as! String
                      if let names = info[Constants.Directory.kName] as? String {
                          name = names
                      }
                      if let childs = info[Constants.Directory.kChild] as? String {
                          child = childs
                      }
  
  
                      if let imgthumb = info[Constants.Directory.kImageThumbnail] as? String {
  
                          imgthumbnail = imgthumb
                      } else {
                          imgthumbnail = ""
                      }
                      if let imgmediumd = info[Constants.Directory.kImageMedium] as? String {
  
                          imgmedium = imgmediumd
                      } else {
                          imgmedium = ""
                      }
  
  
                      if let imglarges = info[Constants.Directory.kImageLarge] as? String {
                          imglarge = imglarges
                      }
  
  
                      let myModel = Directory(
  
                          data: tempInfo,
                          tid: tid,
                          vid: vid,
                          name: name,
                          imgThumbnail: imgthumbnail,
                          imgMedium: imgmedium,
                          imgLarge: "",
                          child: child
  
                      )
  
  
                      self.directorie.append(myModel)
                  }
  

Answer 1

I don't know that this is the only issue, but this code

class func loadSavedFile(fileName: String) -> AnyObject? {
    let pathString: String = Utility.fetchFilePathString(fileName)
    print("Here the pathString is \(pathString)")
    if NSFileManager.defaultManager().fileExistsAtPath(pathString) {
        return NSKeyedUnarchiver.unarchiveObjectWithFile(pathString)!
    } else {
        return "File doesn't exist"
    }
    return ""
}

Either returns an object or a string. That's not very sensible. It should return a success flag or a tuple or use a completion block. When you call this function your code expects to get back an array of directory, which in a number of cases won't happen

self.directorie = (Utility.loadSavedFile(Constants.File.kDirectory) as? [Directory])!

The error in your question indicates a different kind of data mismatch. You should try not to use AnyObject, let swift help you by type checking what you're doing...