How to save array of tuples in UserDefaults

Question

I am using a tuple of arrays in one of my files and want to start saving it in UserDefaults . Here is how I am storing my current data:

typealias savemytuple = (Name: String, NameID: String, BookID: String, Picture: NSData)
var savefun = [savemytuple]()

I have researched and found I may need to do something with the following for saving:

NSKeyedArchiver.archivedDataWithRootObject

And this for retrieving:

NSKeyedUnarchiver.unarchiveObjectWithData

Not sure if this way will work as my tuple has multiple data types. Any idea on how to do this?

Answer 1

The values in UserDefaults must be property lists , so you need to convert each tuple to a property list. A Data is a property list, and there are several ways to convert things to Data .

One way is to stop using a tuple and use a struct instead. If all of the struct 's stored properties conform to Codable , then you can ask Swift to generate everything needed to make the struct itself conform to Codable just by declaring the conformance. Both String and Data conform to Codable .

Once the struct is Codable , you can convert one of them, or even an array of them, into a property list via JSONEncoder or PropertyListEncoder :

import Foundation

struct Bookie: Codable {
    var name: String
    var nameId: String
    var bookId: String
    var picture: Data
}

let bookies = [
    Bookie(name: "mbro12", nameId: "id1", bookId: "b1", picture: Data()),
    Bookie(name: "mayoff", nameId: "id2", bookId: "b2", picture: Data())
]
let bookiesData = try! PropertyListEncoder().encode(bookies)
UserDefaults.standard.set(bookiesData, forKey: "bookies")

let fetchedData = UserDefaults.standard.data(forKey: "bookies")!
let fetchedBookies = try! PropertyListDecoder().decode([Bookie].self, from: fetchedData)
print(fetchedBookies)

Answer 2

You have to convert the tuples into Dictionary to save it, not really a proper way, rather make your tuple into a custom object, then conform NSCoding protocol for a proper way to convert between data and object.

You don't really need NSKeyedArchiver.archivedDataWithRootObject , just simply convert the tuple into a Dictionary and have another function to convert back to the tuple type.