In swift how can I store value of NSUserdefaults which need to store in local database or text file

Question

I am using userdefaults to save data in defaults and now I want to save/transfer that userdefaults data in one text file. Is it possible and if "yes" then how?

Thank you for help and appreciation.

Answer 1

It would work like this example below. You can test it in the Playground:

import UIKit
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

let PersonKey = "PersonKey"
let textFileName = "textFile.txt"
UserDefaults.standard.removeObject(forKey: PersonKey)

class Person: NSObject, NSCoding {
    let name: String
    let age: Int
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
    required init(coder decoder: NSCoder) {
        self.name = decoder.decodeObject(forKey: "name") as? String ?? ""
        self.age = decoder.decodeInteger(forKey: "age")
    }

    func encode(with coder: NSCoder) {
        coder.encode(name, forKey: "name")
        coder.encode(age, forKey: "age")
    }

    func saveToFile() {
        let content = "\(name) \(age)"
        let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
        let documentsDirectory = paths[0]
        let fileName = "\(documentsDirectory)/" + textFileName
        do {
            try content.write(toFile: fileName, atomically: true, encoding: .utf8)
        } catch {
            print(error)
        }
    }

    static func loadDataFromFile() -> String {
        let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
        let documentsDirectory = paths[0]
        let fileName = "\(documentsDirectory)/" + textFileName
        let content: String
        do{
            content = try String(contentsOfFile: fileName, encoding: .utf8)
        }catch _{
            content = ""
        }
        return content;
    }
}

let person = Person(name: "Bob", age: 33)
let ud = UserDefaults.standard

if ud.object(forKey: PersonKey) == nil {
    print("Missing person in UD")
}

let encodedData = NSKeyedArchiver.archivedData(withRootObject: person)
ud.set(encodedData, forKey: PersonKey)

if let data = ud.data(forKey: PersonKey) {
    print("Person data exist")
    let unarchivedPerson = NSKeyedUnarchiver.unarchiveObject(with: data) as? Person
    unarchivedPerson?.saveToFile()
}

let t = DispatchQueue.main.asyncAfter(deadline: .now() + 2.0, execute: {
    print("Data from file: ", Person.loadDataFromFile())
})