SwiftUI: What is @AppStorage property wrapper

Question

I used to save important App data like login credentials into UserDefaults using the following statement:

UserDefaults.standard.set("sample@email.com&quo         


        

Answer 1

Re-implementation for iOS 13 and without SwiftUI

In additon to pawello2222 answer, here. is the reimplementation of the AppStorage that I named it as UserDefaultStorage:

@propertyWrapper
struct UserDefaultStorage {
    private let key: String
    private let defaultValue: T

    private let userDefaults: UserDefaults

    init(key: String, default: T, store: UserDefaults = .standard) {
        self.key = key
        self.defaultValue = `default`
        self.userDefaults = store
    }

    var wrappedValue: T {
        get {
            guard let data = userDefaults.data(forKey: key) else {
                return defaultValue
            }
            let value = try? JSONDecoder().decode(T.self, from: data)
            return value ?? defaultValue
        }
        set {
            let data = try? JSONEncoder().encode(newValue)
            userDefaults.set(data, forKey: key)
        }
    }
}

This wrapper can store/restore any kind of codable into/from the user defaults. Also, it works in iOS 13 and it doesn't need to import SwiftUI.

Usage

@UserDefaultStorage(key: "myCustomKey", default: 0)
var myValue: Int

Note that it can't be used directly as a State