Convert computed property for #State for Swiftui Views - swift

Question

I'm new with SwiftUI and i want to convert basically my computed property for being used in SwiftUI views with combine and all that. I couldn’t use it like that because "get set" doesn't work for my SwiftUI views and I kinda struggled here.
Maybe someone has a good solution how can i convert it with with combine to use in swift ui.
Storage service saves the Authdata into userdefaults.
var currentAuthData: AuthData? {
get {
return self.storageService.get(AuthData.self, forKey: authDataStorageKey)
}
set {
if let value = newValue {
self.storageService.store(value, forKey: authDataStorageKey)
}
}
}

Answer 1

This is how you would turn a computed property in SwiftUI, by making it a #propertyWrapper. I have added a solution to read the data using Combine if you need it. I also make you property optional.
I assume this is the model you want to save.
struct AuthData {
var name: String
var email: String
}
Prepare the protocol for your property wrapper to be able to be set to nil using Optional.
public protocol AnyOptional {
var isNil: Bool { get }
}
extension Optional: AnyOptional {
public var isNil: Bool { self == nil }
}
Extend UserDefaults to conform to this protocol and be optional.
extension UserDefault where Value: ExpressibleByNilLiteral {
init(key: String, _ container: UserDefaults = .standard) {
self.init(key: key, defaultValue: nil, container: container)
}
}
Create the property wrapper that is the same thing as a getter and setter for SwiftUI views. This is a generic one and can be use to any type. You can set them in the UserDefaults extension after this bloc of code.
import Combine
#propertyWrapper
struct UserDefault<Value> {
let key: String
let defaultValue: Value
var container: UserDefaults = .standard
// Set a Combine publisher for your new value to
// always read its changes when using Combine.
private let publisher = PassthroughSubject<Value, Never>()
var wrappedValue: Value {
get {
// Get the new value or nil if any.
container.object(forKey: key) as? Value ?? defaultValue
}
set {
// Check if the value is nil and remove it from your object.
if let optional = newValue as? AnyOptional, optional.isNil {
container.removeObject(forKey: key)
}
else {
// Set your new value inside UserDefaults.
container.set(newValue, forKey: key)
}
// Add the newValue to your combine publisher
publisher.send(newValue)
}
}
var projectedValue: AnyPublisher<Value, Never> {
publisher.eraseToAnyPublisher()
}
}
Create the extension in UserDefaults to use your property wrapper in your code.
extension UserDefaults {
#UserDefault(key: "authDataStorageKey", defaultValue: nil)
static var savedAuthData: AuthData?
// You can create as many #propertyWrapper as you want that fits your need
}
examples of use
// Set a new value
UserDefaults.savedAuthData = AuthData(name: "Muli", email: "muli#stackoverflow.com")
// Read the saved value
print(UserDefaults.savedAuthData as Any)
// When using combine
var subscriptions = Set<AnyCancellable>()
UserDefaults.$savedAuthData
.sink { savedValue in
print(savedValue as Any) } // Yours saved value that changes over time.
.store(in: &subscriptions)