Append things to Array at launching - ios

Question

Hi have a question to the following code:
struct ContentView: View {
#State private var listItems = [Item]()
let savedItems = UserDefaults.standard.string(forKey: "Items") ?? "error"
var body: some View {
NavigationView{
List{
ForEach(listItems){ item in
Text(item.name)
}
NavigationLink(
destination: AddView(listItems: $listItems),
label: {
Text(" Add")
.foregroundColor(.blue)
})
}
.navigationBarTitle("MyApp")
}
}
}
struct AddView: View {
#State var text:String = ""
#Binding var listItems: [Item]
var body: some View {
VStack{
TextField("Name", text: $text).padding().background(Color(.systemGray5)).frame(width: 400,alignment: .center).cornerRadius(20)
Button(action: {
listItems.append(Item(name: text, image: "Gif"))
print(listItems)
UserDefaults.standard.set(listItems, forKey: "Items")
}, label: {
Text("Add")
})
}
}
}
If i append something in the AddView, i want to save it in the UserDefaults and append it automatically when the app starts. But I don't know how to do this. Can you help me ?
PS: I'm using AppDelegate and SceneDelegate.

Answer 1

To save something in the UserDefaults it will need to be either of those things:
The value parameter can be only property list objects: NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary. For NSArray and NSDictionary objects, their contents must be property list objects.
see full documentation
You are trying assign and array of Item objects, and while it is perfectly fine to save an array, the Element type of this array will also need to be one of the types mentioned in the documentation.
Your problem can be solved using Codable conformance.
Extend your item type with Codable
struct Item: Codable {
/// your implementation
}
Save encoded items to UserDefaults
extension UserDefaults {
func saveItems(_ items: [Item]) {
let encoder = JSONEncoder()
if let data = try? encoder.encode(items) {
set(data, forKey: "Items")
}
}
}
simply call this method anytime you want to save listItems array.
UserDefaults.standard.saveItems(listItems)
Read stored items from UserDefaults
extension UserDefaults {
func readItems() -> [Item]? {
guard let data = value(forKey: "Items") as? Data else {
return nil
}
let decoder = JSONDecoder()
return try? decoder.decode([Item].self, from: data)
}
}
with this method you can lazily load items when you need them
#State private var listItems = UserDefaults.standard.readItems() ?? []