ContentView2.swift

ContentView2.swift

import SwiftUI

struct ContentView: View {
        
    @StateObject var settings = Settings()
    
    var body: some View {
        VStack(spacing: 20) {
            Text(settings.isActive ? "Yes" : "No")
            Button("Toogle") {
                settings.isActive.toggle()
            }
        }
    }
    
}

class Settings: ObservableObject {
    
    @Persistent(key: "isActive")
    var isActive: Bool = false
    
}

@propertyWrapper
struct Persistent<Value>: DynamicProperty {
    let key: String
    let defaultValue: Value
    let store: UserDefaults
    
    init(
        wrappedValue defaultValue: Value,
        key: String,
        store: UserDefaults = .standard
    ) {
        self.defaultValue = defaultValue
        self.key = key
        self.store = store
        self.value = State<Value>(
            initialValue: store.object(forKey: key) as? Value ?? defaultValue
        )
    }
    
    private var value: State<Value>
    
    var wrappedValue: Value {
        get {
            value.wrappedValue
        }
        nonmutating set {
            DispatchQueue.main.async {
                value.wrappedValue = newValue
                if let optional = newValue as? AnyOptional, optional.isNil {
                    store.removeObject(forKey: key)
                } else {
                    store.set(newValue, forKey: key)
                }
            }
        }
    }

    var projectedValue: Binding<Value> {
        value.projectedValue
    }
}

extension Persistent where Value: ExpressibleByNilLiteral {
    init(key: String, store: UserDefaults = .standard) {
        self.init(wrappedValue: nil, key: key, store: store)
    }
}

protocol AnyOptional {
    var isNil: Bool { get }
}

extension Optional: AnyOptional {
    var isNil: Bool { self == nil }
}