How To Add [int:int] element in user Defaults in swift5 - ios

Question

I used to many attempts to solve this error but i can't.
i have [Int: Int] dictionary
want's to add this dictionary to default for use latter
Sample Code Of mine
var ListIds = [Int: Int]()
ListIds[1] = 1
defaults.set(["data": ListIds], forKey: "cartKeys")

Answer 1

Some quick web searching and I found this: Hacking with Swift forums - Save [Int:Int] to UserDefaults
I edited the code slightly to make it an extension, and to allow passing the Key to use in UserDefaults:
extension UserDefaults {
func saveIntDictionary(key: String, intDictionary: [Int:Int]) {
let encoder = PropertyListEncoder()
guard let data = try? encoder.encode(intDictionary) else {
return
}
set(data, forKey: key)
}
func retrieveSavedIntDictionary(key: String) -> [Int:Int]? {
let decoder = PropertyListDecoder()
guard let data = data(forKey: key),
let intDictionary = try? decoder.decode([Int:Int].self, from: data) else {
return nil
}
return intDictionary
}
}
and it can be used like this:
// note: it returns an optional -- it will be nil if the key does not exist
// handle that appropriately
let sv = UserDefaults.standard.retrieveSavedIntDictionary(key: "cartKeys")
// save to UserDefaults
UserDefaults.standard.saveIntDictionary(key: "cartKeys", intDictionary: listIDs)
Here's a quick runnable example:
class ViewController: UIViewController {
var listIDs: [Int : Int] = [:]
// a scrollable non-editable text view to display the dictionary
let displayTextView = UITextView()
override func viewDidLoad() {
super.viewDidLoad()
if let sv = UserDefaults.standard.retrieveSavedIntDictionary(key: "cartKeys") {
listIDs = sv
print("Loaded from UserDefaults!")
print(String(describing: listIDs))
print()
} else {
print("Nothing in UserDefaults")
print()
}
// let's have two buttons
// Add a new ID
// Reset (clears the dictionary)
let b1 = UIButton()
b1.setTitle("Add a new ID", for: [])
b1.setTitleColor(.white, for: .normal)
b1.setTitleColor(.lightGray, for: .highlighted)
b1.backgroundColor = .systemBlue
b1.layer.cornerRadius = 8
b1.addTarget(self, action: #selector(addEntry(_:)), for: .touchUpInside)
let b2 = UIButton()
b2.setTitle("Reset", for: [])
b2.setTitleColor(.white, for: .normal)
b2.setTitleColor(.lightGray, for: .highlighted)
b2.backgroundColor = .systemRed
b2.layer.cornerRadius = 8
b2.addTarget(self, action: #selector(reset(_:)), for: .touchUpInside)
displayTextView.backgroundColor = .yellow
displayTextView.font = .monospacedSystemFont(ofSize: 16.0, weight: .regular)
displayTextView.isEditable = false
// a stack view for the buttons and display text view
let stack = UIStackView(arrangedSubviews: [b1, displayTextView, b2])
stack.axis = .vertical
stack.spacing = 12
stack.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(stack)
let g = view.safeAreaLayoutGuide
NSLayoutConstraint.activate([
stack.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 40.0),
stack.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -40.0),
stack.centerYAnchor.constraint(equalTo: g.centerYAnchor, constant: -20.0),
displayTextView.heightAnchor.constraint(equalToConstant: 240.0),
])
updateDisplay()
}
func updateDisplay() {
var s: String = ""
if listIDs.isEmpty {
s = "No entries in listIDs"
} else {
listIDs.forEach { item in
s += "Key: \(item.key)\t\tValue: \(item.value)\n"
}
}
displayTextView.text = s
}
#objc func addEntry(_ sender: Any?) {
// add a new entry
let n: Int = listIDs.count + 1
let v: Int = Int.random(in: 1...20000)
listIDs[n] = v
// save to UserDefaults
UserDefaults.standard.saveIntDictionary(key: "cartKeys", intDictionary: listIDs)
updateDisplay()
}
#objc func reset(_ sender: Any?) {
// clear the dictionary
listIDs = [:]
// save to UserDefaults
UserDefaults.standard.removeObject(forKey: "cartKeys")
//UserDefaults.standard.saveIntDictionary(key: "cartKeysA", intDictionary: listIDs)
updateDisplay()
}
}
When run, it will look like this. Each tap of "Add a new ID" will add a new sequential entry to the dictionary (with a random value) and save to UserDefaults. Quit the app and re-run it to see the dictionary loaded. Tap "Reset" to clear it:
A couple notes:
1 - Learn about naming conventions... listIDs instead of ListIds for example.
2 - Saving "data" this way is generally not a good idea -- UserDefaults is much better suited to storing things like "app settings" for example. If your dictionary of "IDs" may grow large, you probably want to look at other data persistence methods.