What new monitoring and state management tools have been introduced in SwiftUI after iOS 13?

After iOS 13, new tools for monitoring and managing state were added to SwiftUI, expanding the capabilities of reactive programming:

• @StateObject — for creating and managing the lifecycle of ObservableObject instances within a view, ensuring the object is created only once.
• @ObservedObject — for subscribing to changes in external ObservableObject.
• @EnvironmentObject — for passing data through the view hierarchy without explicit passing.
• @AppStorage — for conveniently binding state to UserDefaults.
• @SceneStorage — for preserving state within the scene's lifecycle.

These properties allow for efficient tracking of data changes and automatic UI updates without additional code.

Example of using @StateObject:

class ViewModel: ObservableObject {
    @Published var count = 0
}

struct ContentView: View {
    @StateObject private var viewModel = ViewModel()

    var body: some View {
        VStack {
            Text("Count: \(viewModel.count)")
            Button("Increment") {
                viewModel.count += 1
            }
        }
    }
}