Save & Retrieve TableViewCell checkmark using NSUserDefaults in Swift

Question

I am trying to save and retrieve tableViewCell checkmark using NSUserDefaults.My partial code as below.From the code,I can able to select or deselect cell using UITableViewC

Answer 1

• First of all create a class Item as data source with a name and selected property.

  class Item {
    let name : String
    var selected = false
  
    init(name: String) {
      self.name = name
    }
  }
  

• Declare the data source array

  var myItems = [Item]()
  

• Create the items this way

  let item = Item(name:"Foo") // your former string value, `selected` is false by default.
  myItems.append(item)
  

• In applicationDidFinishLaunching register an empty string array as default value for key selectedCells

  let defaults = NSUserDefaults.standardUserDefaults()
  let defaultValues = ["selectedCells" : [String]()]
  defaults.registerDefaults(defaultValues)
  

• To read all selected cells from user defaults get the string array and set the property selected of all corresponding items to true. Then reload the table view. The forced unwrapping is safe because the key/value is pre-registered and always non-optional. Important: Make sure that readDefaults() is always called after registering the default values.

  func readDefaults()
  {
    let defaults = NSUserDefaults.standardUserDefaults()
    let selectedItems = defaults.stringArrayForKey("selectedCells")!
    for item in myItems {
      item.selected = selectedItems.contains(item.name)
    }
    tableView.reloadData()
  }
  

• In cellForRowAtIndexPath set both properties accordingly

  func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
  
    let cell = tableView.dequeueReusableCellWithIdentifier("MyCell", forIndexPath: indexPath)
    let item = myItems[indexPath.row]
    cell.textLabel!.text = item.name
    cell.accessoryType = item.selected ? .Checkmark : .None
    cell.selectionStyle = .None
    cell.tintColor = UIColor.greenColor()
  
    return cell
  }
  

• To save the data filter all items whose selected property is true, map it to the names and save the array.

  func saveDefaults() {
    let selectedCells = myItems.filter { $0.selected }.map { $0.name }
    let defaults = NSUserDefaults.standardUserDefaults()
    defaults.setObject(selectedCells, forKey:"selectedCells")
  }
  

• Now you should change the model in didSelectRowAtIndexPath and reload the row. This is much more efficient (and recommended) than manipulating the cell

  func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
    let item = myItems[indexPath.row]
    item.selected = true
    tableView.reloadRowsAtIndexPaths([indexPath], withRowAnimation: .None)
  }
  

Answer 2

My example, i Load in tableView set in DetailController

Model ----

struct TheoryData {

    var id: String
    var theoryText: String
    var theoryModes: String
    var theoryImage: String
    var like: Bool
}

Read values

   var theoryData = [TheoryData]()

private func readDefaults() {
    let defaults = UserDefaults.standard
    let selectedItems = defaults.stringArray(forKey: "selectedCells") ?? []
    
    (0..<theoryData.count).forEach { i in
        theoryData[i].like = selectedItems.contains(theoryData[i].id)
    }
    menuTableView.reloadData()
}

 override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    readDefaults()
}

In cell

let theory = theoryData[indexPath.row]
cell.likeImage.image = theory.like ? #imageLiteral(resourceName: "heart-icon") : #imageLiteral(resourceName: "heart-empty-icon")

Save state in UserDefault

    @IBAction func likeButtonTapped(_ sender: UIButton) {
        theoryData.like.toggle()
        let likeIcon = theoryData.like ? #imageLiteral(resourceName: "heart-icon") : #imageLiteral(resourceName: "heart-empty-icon")
        likeButton.setImage(likeIcon, for: .normal)
        saveSelection()
    }
    
    private func saveSelection() {
        let defaults = UserDefaults.standard
        var selectedItems = defaults.stringArray(forKey: "selectedCell") ?? []
        
        if theoryData.like {
            selectedItems.append(theoryData.id)
        } else {
            selectedItems = selectedItems.filter{ $0 != theoryData.id }
        }
        print(selectedItems)
        defaults.setValue(selectedItems, forKey: "selectedCell")
    }
 }