This example will show you how to use property wrappers to save Codable objects into UserDefaults

TaskPropertyWrapper.swift

import Foundation

struct Task: Codable {
    var title: String
    var isDone: Bool
}

enum Errors: Error {
    case encodeError
    case decodeError
    case noUserDefaults
}

func saveTask(_ task: Task, forKey key: String) throws {
    let userDefaults = UserDefaults.standard
    let encoder = JSONEncoder()
    do {
        let data = try encoder.encode(task)
        userDefaults.set(data, forKey: key)
        userDefaults.synchronize()
    } catch {
        throw(Errors.encodeError)
    }
}

func getTask(forKey key: String) throws -> Task? {
    let userDefaults = UserDefaults.standard
    let decoder = JSONDecoder()
    guard let data = userDefaults.object(forKey: key) as? Data else {
        throw(Errors.noUserDefaults)
    }
    do {
        let task = try decoder.decode(Task.self, from: data)
        return task
    } catch {
        throw(Errors.decodeError)
    }
}

@propertyWrapper
struct UserDefaultsWrapper<Value: Codable> {
    let key: String
    let defaultValue: Value
    let userDefaults = UserDefaults.standard

    var wrappedValue: Value {
        get {
            let data = userDefaults.data(forKey: key)
            let value = data.flatMap { try? JSONDecoder().decode(Value.self, from: $0) }
            return value ?? defaultValue
        }

        set {
            let data = try? JSONEncoder().encode(newValue)
            userDefaults.set(data, forKey: key)
            userDefaults.synchronize()
        }
    }
}


let defaultTasks: [Task] = [
    Task(title: "Learn SwiftUI", isDone: false),
    Task(title: "Share this article", isDone: true)
]

struct TaskProvider {
    @UserDefaultsWrapper(key: "Tasks", defaultValue: defaultTasks)
    var tasks: [Task]

}

var provider = TaskProvider()

dump(provider.tasks)

provider.tasks.append(Task(title: "Code in Swift", isDone: true))

dump(provider.tasks)