Make ObservableObject subscribe to custom PropertyWrapper - swift

Question

I have written a custom PropertyWrapper, that tries to wrap UserDefaults while also giving them the same behaviour as a #Published variable. It almost works, except that the ObservableObject does not propagate the changes without observing the UserDefaults themselves.
I cannot pass a objectWillChange ref to the #Setting init, as self is not available during Settings.init...
I wonder how #Published does that..
import Combine
import Foundation
class Settings: ObservableObject {
// Trying to avoid this:
/////////////////////////////////////////////
let objectWillChange = PassthroughSubject<Void, Never>()
private var didChangeCancellable: AnyCancellable?
private init(){
didChangeCancellable = NotificationCenter.default
.publisher(for: UserDefaults.didChangeNotification)
.map { _ in () }
.receive(on: DispatchQueue.main)
.subscribe(objectWillChange)
}
/////////////////////////////////////
static var shared = Settings()
#Setting(key: "isBla") var isBla = true
}
#propertyWrapper
public struct Setting<T> {
let key: String
let defaultValue: T
init(wrappedValue value: T, key: String) {
self.key = key
self.defaultValue = value
}
public var wrappedValue: T {
get {
let val = UserDefaults.standard.object(forKey: key) as? T
return val ?? defaultValue
}
set {
objectWillChange?.send()
publisher?.subject.value = newValue
UserDefaults.standard.set(newValue, forKey: key)
}
}
public struct Publisher: Combine.Publisher {
public typealias Output = T
public typealias Failure = Never
public func receive<Downstream: Subscriber>(subscriber: Downstream)
where Downstream.Input == T, Downstream.Failure == Never {
subject.subscribe(subscriber)
}
fileprivate let subject: Combine.CurrentValueSubject<T, Never>
fileprivate init(_ output: Output) {
subject = .init(output)
}
}
private var publisher: Publisher?
internal var objectWillChange: ObservableObjectPublisher?
public var projectedValue: Publisher {
mutating get {
if let publisher = publisher {
return publisher
}
let publisher = Publisher(wrappedValue)
self.publisher = publisher
return publisher
}
}
}