A SwiftUI based Playground for SwiftUI store management

SwiftUIStoreManagement.swift

//: A SwiftUI based Playground for SwiftUI store management
  
import SwiftUI
import PlaygroundSupport
import Observation


struct ContentView: View {
  @State private var name: String = ""
  @State private var title: String = ""

  var body: some View {
    VStack {
      Button {
        name = UUID().uuidString
        title = UUID().uuidString
      } label: {
        Text("Click me")
      }

      MyInitializableView(name: name, title: title)
//        .id(name)

      MyView()
    }
    .frame(minWidth: 300, minHeight: 400)
  }
}

class DataModel: ObservableObject {
  @Published var name = "Some Name"
  @Published var isEnabled = false

  init(name: String = "Some Name", isEnabled: Bool = false) {
    self.name = name
    self.isEnabled = isEnabled
  }
}

class Library {
  var name = ""
  init(name: String = "My library of books") {
    let seconds = 4.0
    DispatchQueue.main.asyncAfter(deadline: .now() + seconds) {
      self.name = name
      print("Library Init: name = \(name)")
    }
  }
}


struct MyInitializableView: View {
  let title: String
  @State private var state: String = "Hello"
  @StateObject private var model: DataModel

  @State private var library: Library? = Library(name: "Init Library inline")

  init(name: String, title: String) {
    // SwiftUI ensures that the following initialization uses the
    // closure only once during the lifetime of the view, so
    // later changes to the view's name input have no effect.
    _model = StateObject(wrappedValue: DataModel(name: name))
//    self.model = DataModel(name: name) // Compiler error
//    state = "Why don not update me" // The same with StateObject
    print("MyInitializableView init")
    self.title = title
  }


  var body: some View {
    let _ = Self._printChanges()
    VStack {
      Text("Name: \(model.name)")
      Text("title: \(title)")
      Text("state: \(state)")

      if let library {
        Text(library.name)
      }
    }
    .onAppear {
      print("MyInitializableView onAppear")
      state = "World"
    }
    .task {
      print("MyInitializableView task")
      library = Library(name: "Init Library in task")
    }
  }
}

struct MyView: View {
  @StateObject private var model = DataModel(name: "My View inline")
  @State private var title: String = ""

  var body: some View {
    Text(model.name)
    Button("Change title") {
      title = UUID().uuidString
    }
    MySubView(model: model, title: title)
      .onChange(of: model.isEnabled) { oldValue, newValue in
        title = UUID().uuidString
      }
  }
}


struct MySubView: View {
  @ObservedObject var model: DataModel
  let title: String

  init(model: DataModel, title: String) {
    print("MySubView init")
    self.model = model
//    self.model = DataModel(name: "MySubView init") // Will change model when init runs
//    self._model = ObservedObject(wrappedValue: DataModel(name: "MySubView init _model"))  // Will change model when init runs


    self.title = title
  }

  var body: some View {
    Group {
      Text("MySubView title: \(title)")
      Text("MySubView name: \(model.name)")
      Toggle("Enabled", isOn: $model.isEnabled)
    }
    .task {
      self.model.name = "From My subview task init"
    }
  }
}

PlaygroundPage.current.setLiveView(ContentView())