Error when trying to save to NSUserdefaults

Question

I have a table which works in the following way. If a row is selected, an amount corresponding to the selected row is added to var total, a checkmark is added. If it is deselected, the amount will be subtracted, the checkmark will be set to none. My code worked properly before trying to save/retrieve the data to/from NSUserDefaults. The errors are: when I select the first row, it subtracts the amount instead of adding it; after a row is selected, if I tap on the back button and then come back to same screen the checkmark is not displayed. In this construct when I try to retrieve from NSUserDefaults indexPathForCellSelected evaluates to nil even though I check if indexPathForCellSelected != nil before making the assignment. fatal error: unexpectedly found nil while unwrapping an Optional value

if indexPathForCellSelected != nil { self.tableView.cellForRowAtIndexPath(indexPathForCellSelected!)?.
accessoryType = .Checkmark
}



class NinethViewController: UIViewController, UITableViewDelegate,UITableViewDataSource {

var total = 0
var indexRowRetrieved:Int?
var rowSelected:Int?
var indexRowSelectedKey = "indexRowKey"
var amountKey = "amountKey"
var totalKey = "totalKey"
let indexPathKey = "indexPathForCellSelected"
var indexPathForCellSelected: NSIndexPath?


struct Item {
    var name:String // name of the row
    var selected:Bool // whether is selected or not
    var amount: Int // value of the item
}

var extras = [

    Item(name:"Inside Cabinets",selected: false, amount: 5),
    Item(name:"Inside Fridge",selected: false, amount: 5),
    Item(name:"Inside Oven",selected: false, amount: 5),
    Item(name:"Laundry wash & dry",selected: false, amount: 10),
    Item(name:"Interior Windows", selected: false, amount: 5)
]


@IBOutlet weak var tableView: UITableView!

override func viewDidLoad() {
    super.viewDidLoad()
}

override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)

    // loadData from NSUserDefaults
    loadData()
}

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return extras.count
}

func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    return 1
}

// configure the cell
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath)
    -> UITableViewCell     {
        let cell = tableView.dequeueReusableCellWithIdentifier("Cell")
        cell?.textLabel?.text = extras[indexPath.row].name
        return cell!
}

func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {

    // if the cell has not been selected before
    if !extras[indexPath.row].selected  {

        // marks the cell as selected
        extras[indexPath.row].selected = true
        tableView.cellForRowAtIndexPath(indexPath)?.accessoryType = .Checkmark

        self.total += extras[indexPath.row].amount
        indexPathForCellSelected = indexPath
        rowSelected = indexPath.row
        print(total)

        //   save all info in NSUserDefaults
                saveData()

    } else {
        // marks the cell as not selected
        extras[indexPath.row].selected = false
        tableView.cellForRowAtIndexPath(indexPath)?.accessoryType = .None

        self.total -= extras[indexPath.row].amount
        print(total)



    }
}


func saveData(){

    // save indexPathForCellSelected in NSUserDefaults
    if indexPathForCellSelected != nil {
         let data = NSKeyedArchiver.archivedDataWithRootObject(indexPathForCellSelected!)
                     NSUserDefaults.standardUserDefaults().setObject(data, forKey: indexPathKey)

        // save indexRowSelected
        NSUserDefaults.standardUserDefaults().setInteger(rowSelected!, forKey: indexRowSelectedKey)

        // save amount for corresponding row in NSUserDefaults
        NSUserDefaults.standardUserDefaults().setObject(extras[rowSelected!].amount, forKey: amountKey)

        //save total in NSUserDefaults
        NSUserDefaults.standardUserDefaults().setObject(total, forKey: totalKey)

    }

}



func loadData() {
    //retrieve indexPathForCellSelected from NSUserDefaults
    if let retrievedIndexPath = NSUserDefaults.standardUserDefaults().dataForKey(indexPathKey) {
        if let data1 = NSKeyedUnarchiver.unarchiveObjectWithData(retrievedIndexPath) as? NSIndexPath{
            indexPathForCellSelected = data1
        }
    }


    // retrieve the index for row selected to select the state of the row: true or false
    if let retrievedIndexRow = NSUserDefaults.standardUserDefaults().integerForKey(indexRowSelectedKey) as? Int      {
            indexRowRetrieved = retrievedIndexRow
                extras[retrievedIndexRow].selected = true
    }

    // retrieve amount for corresponding row in NSUserDefaults
    if let itemAmount =  NSUserDefaults.standardUserDefaults().objectForKey(amountKey) as? Int {
        extras[indexRowRetrieved!].amount = itemAmount

        // assign checkmark to row selected
            if indexPathForCellSelected != nil {
                self.tableView.cellForRowAtIndexPath(indexPathForCellSelected!)?.accessoryType = .Checkmark
        }
    }
    // retrieve total from NSUserDefaults
        if let totalRetrieved = NSUserDefaults.standardUserDefaults().objectForKey(totalKey) as? Int {
            total = totalRetrieved
                print(total)
      }
   }
}

Answer 1

I don't know why you are saving all the NSIndexPath's for the cells selected previously when according your previous question and this one, you need to save only the index of the cell selected and the value of the total you had when you go to another controller. You can do it in the following way:

var frequency = [
    Item(name:"Every week",selected: false, amount: 30),
    Item(name:"Every 2 weeks",selected: false, amount: 30),
    Item(name:"Every 4 weeks",selected: false, amount: 30),
    Item(name:"Once",selected: false, amount: 40),
    Item(name:"End of tenancy cleaning", selected: false, amount: 44)
]

var indexPathForCellSelected: NSIndexPath?
var total = 0

let indexPathKey = "indexPathForCellSelectedNinethViewControllerKey"
let totalKey = "totalNinethViewControllerKey"

override func viewDidLoad() {
    super.viewDidLoad()

    loadData()
}

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath)
    cell.textLabel?.text = frequency[indexPath.row].name
    if let _ = indexPathForCellSelected where indexPath == indexPathForCellSelected {
        cell.accessoryType = .Checkmark
    }
    return cell
}

func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {

    if !frequency[indexPath.row].selected {

        // this avoid set initial value for the first time
        if let index = indexPathForCellSelected {
            // clear the previous cell
            frequency[index.row].selected = false
            tableView.cellForRowAtIndexPath(index)?.accessoryType = .None
            self.total -= frequency[index.row].amount
        }

        // mark the new one
        frequency[indexPath.row].selected = true
        tableView.cellForRowAtIndexPath(indexPath)?.accessoryType = .Checkmark

        indexPathForCellSelected = indexPath
        self.total += frequency[indexPath.row].amount

        saveData()
    }
}

private func saveData() {

    // save the index for the cell selected in NSUserDefaults
    NSUserDefaults.standardUserDefaults().setInteger(indexPathForCellSelected!.row, forKey: indexPathKey)

    // save total in NSUserDefaults
    NSUserDefaults.standardUserDefaults().setInteger(total, forKey: totalKey)
}

private func loadData() {

    // get the values from NSUserDefaults if exist
    if let indexValue = NSUserDefaults.standardUserDefaults().valueForKey(indexPathKey), totalValue = NSUserDefaults.standardUserDefaults().valueForKey(totalKey) {
        indexPathForCellSelected = NSIndexPath(forRow: indexValue as! Int, inSection: 0)
        total = totalValue as! Int
    }
}

I hope this help you.