swiftui_update_inconsistency.swift

// SOME OBSERVATIONS:
// * In Xcode 11.3.1 `V_Struct_Representable_ObservedObject` won't update
//   which is clearly a bug. This bug is fixed in Xcode 11.4 beta 1.
//
// * `V_Struct` and `V_Struct_Representable` both never update because
//   they shouldn't as the framework internal raw-diffing likely won't
//   identify any change. (EXPECTED BEHAVIOR)
//
// * `V_Class` and `V_Class_ObservedObject` both produce a runtime crash,
//   which might be a bug as well. `View` conforming types shouldn't be
//   classes, yet both `UIViewRepresentable` and 
//   `UIViewControllerRepresentable` can be classes and they don't crash.
//   Therefore this seems like another bug.
//

import Combine
import SwiftUI
import UIKit

// Helper

func createUILabel() -> UILabel {
  let label = UILabel()
  label.textAlignment = .center
  return label
}

func log<T>(_ t: T, function: StaticString = #function) {
  print("\(function) 🔸 \(type(of: t))")
}

func log<T>(_ t: T, function: StaticString = #function) where T: AnyObject {
  print("\(function) 🔹 \(type(of: t)) 🔹 \(ObjectIdentifier(t))")
}

protocol P: View {
  init(model: Model)
}

class VC: UIViewController {
  let label = createUILabel()
  override func loadView() {
    view = label
  }
}

// Model

class Model: ObservableObject {
  let objectWillChange = ObservableObjectPublisher()

  var count = 0 {
    willSet {
      objectWillChange.send()
    }
  }

  var _timer: Timer?

  init() {
    self._timer = Timer.scheduledTimer(
      timeInterval: 2,
      target: self,
      selector: #selector(_countUp),
      userInfo: nil,
      repeats: true
    )
  }

  @objc
  func _countUp() {
    count += 1
  }
}

// Different view structs

struct V_Struct: View, P {
  var model: Model

  init(model: Model) {
    self.model = model
    log(self)
  }

  var body: some View {
    log(self)
    return Text("\(model.count)")
  }
}

struct V_Struct_ObservedObject: View, P {
  @ObservedObject
  var model: Model

  init(model: Model) {
    self.model = model
    log(self)
  }

  var body: some View {
    log(self)
    return Text("\(model.count)")
  }
}

struct V_Struct_Representable: UIViewRepresentable, P {
  var model: Model

  init(model: Model) {
    self.model = model
    log(self)
  }

  func makeUIView(context: Context) -> UILabel {
    log(self)
    return createUILabel()
  }

  func updateUIView(_ uiView: UILabel, context: Context) {
    log(self)
    uiView.text = "\(model.count)"
  }
}

struct V_Struct_Representable_ObservedObject: UIViewRepresentable, P {
  @ObservedObject
  var model: Model

  init(model: Model) {
    self.model = model
    log(self)
  }

  func makeUIView(context: Context) -> UILabel {
    log(self)
    return createUILabel()
  }

  func updateUIView(_ uiView: UILabel, context: Context) {
    log(self)
    uiView.text = "\(model.count)"
  }
}

// Different view classes

final class V_Class: View, P {
  var model: Model

  init(model: Model) {
    self.model = model
    log(self)
  }

  deinit {
    log(self)
  }

  var body: some View {
    log(self)
    return Text("\(model.count)")
  }
}

final class V_Class_ObservedObject: View, P {
  @ObservedObject
  var model: Model

  init(model: Model) {
    self.model = model
    log(self)
  }

  deinit {
    log(self)
  }

  var body: some View {
    log(self)
    return Text("\(model.count)")
  }
}

final class V_Class_Representable: UIViewRepresentable, P {
  var model: Model

  init(model: Model) {
    self.model = model
    log(self)
  }

  deinit {
    log(self)
  }

  func makeUIView(context: Context) -> UILabel {
    log(self)
    return createUILabel()
  }

  func updateUIView(_ uiView: UILabel, context: Context) {
    log(self)
    uiView.text = "\(model.count)"
  }
}

final class V_Class_Representable_ObservedObject: UIViewRepresentable, P {
  @ObservedObject
  var model: Model

  init(model: Model) {
    self.model = model
    log(self)
  }

  deinit {
    log(self)
  }

  func makeUIView(context: Context) -> UILabel {
    log(self)
    return createUILabel()
  }

  func updateUIView(_ uiView: UILabel, context: Context) {
    log(self)
    uiView.text = "\(model.count)"
  }
}

final class VC_Class_Representable: UIViewControllerRepresentable, P {
  var model: Model

  init(model: Model) {
    self.model = model
    log(self)
  }

  deinit {
    log(self)
  }

  func makeUIViewController(context: Context) -> VC {
    log(self)
    return VC()
  }

  func updateUIViewController(_ uiViewController: VC, context: Context) {
    log(self)
    uiViewController.label.text = "\(model.count)"
  }
}

final class VC_Class_Representable_ObservedObject:
  UIViewControllerRepresentable,
  P
{
  @ObservedObject
  var model: Model

  init(model: Model) {
    self.model = model
    log(self)
  }

  deinit {
    log(self)
  }

  func makeUIViewController(context: Context) -> VC {
    log(self)
    return VC()
  }

  func updateUIViewController(_ uiViewController: VC, context: Context) {
    log(self)
    uiViewController.label.text = "\(model.count)"
  }
}

// Test

struct ContentView: View {
  @ObservedObject
  var model: Model = Model()

  func create<T>(_ tType: T.Type) -> some View where T: P {
    VStack
      .init {
        Text(String(describing: tType)).font(.system(size: 10))
        tType.init(model: model).frame(width: 100, height: 20)
      }
      .border(Color.red)
      .fixedSize()
  }

  var body: some View {
    print("\n🟢", #function, type(of: self), "\n")
    return VStack {
      Group {
        Text("value views")
        create(V_Struct.self)
        create(V_Struct_ObservedObject.self)
        create(V_Struct_Representable.self)
        create(V_Struct_Representable_ObservedObject.self)
      }
      Group {
        Text("object views")
        // Runtime crash: EXC_BAD_INSTRUCTION
        // create(V_Class.self)
        // create(V_Class_ObservedObject.self)
        create(V_Class_Representable.self)
        create(V_Class_Representable_ObservedObject.self)
        create(VC_Class_Representable.self)
        create(VC_Class_Representable_ObservedObject.self)
      }
    }
  }
}

struct ContentView_Previews: PreviewProvider {
  static var previews: some View {
    ContentView()
  }
}


/* SOME CYCLES IN XCODE 11.3.1:

🟢 body ContentView 

init(model:) 🔸 V_Struct
init(model:) 🔸 V_Struct_ObservedObject
init(model:) 🔸 V_Struct_Representable
init(model:) 🔸 V_Struct_Representable_ObservedObject
init(model:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x000060000025fba0)
init(model:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000238660)
init(model:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600000238760)
init(model:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x00006000002382a0)
body 🔸 V_Struct
body 🔸 V_Struct_ObservedObject
makeUIView(context:) 🔸 V_Struct_Representable
updateUIView(_:context:) 🔸 V_Struct_Representable
makeUIView(context:) 🔸 V_Struct_Representable_ObservedObject
updateUIView(_:context:) 🔸 V_Struct_Representable_ObservedObject
makeUIView(context:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x000060000025fba0)
updateUIView(_:context:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x000060000025fba0)
makeUIView(context:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000238660)
updateUIView(_:context:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000238660)
makeUIViewController(context:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600000238760)
updateUIViewController(_:context:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600000238760)
makeUIViewController(context:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x00006000002382a0)
updateUIViewController(_:context:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x00006000002382a0)

🟢 body ContentView 

init(model:) 🔸 V_Struct
init(model:) 🔸 V_Struct_ObservedObject
init(model:) 🔸 V_Struct_Representable
init(model:) 🔸 V_Struct_Representable_ObservedObject
init(model:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600000238da0)
init(model:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000238f20)
init(model:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600000238f40)
init(model:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000238f80)
body 🔸 V_Struct_ObservedObject
updateUIView(_:context:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600000238da0)
updateUIView(_:context:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000238f20)
updateUIViewController(_:context:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600000238f40)
updateUIViewController(_:context:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000238f80)
deinit 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x000060000025fba0)
deinit 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000238660)
deinit 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600000238760)
deinit 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x00006000002382a0)

🟢 body ContentView 

init(model:) 🔸 V_Struct
init(model:) 🔸 V_Struct_ObservedObject
init(model:) 🔸 V_Struct_Representable
init(model:) 🔸 V_Struct_Representable_ObservedObject
init(model:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600000238660)
init(model:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000239540)
init(model:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600000238760)
init(model:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x00006000002384c0)
body 🔸 V_Struct_ObservedObject
updateUIView(_:context:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600000238660)
updateUIView(_:context:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000239540)
updateUIViewController(_:context:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600000238760)
updateUIViewController(_:context:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x00006000002384c0)
deinit 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600000238da0)
deinit 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000238f20)
deinit 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600000238f40)
deinit 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600000238f80)

*/

/* SOME CYCLES IN XCODE 11.4 beta 1:

🟢 body ContentView 

init(model:) 🔸 V_Struct
init(model:) 🔸 V_Struct_ObservedObject
init(model:) 🔸 V_Struct_Representable
init(model:) 🔸 V_Struct_Representable_ObservedObject
init(model:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600002d8ecc0)
init(model:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d8ec40)
init(model:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600002d8ed00)
init(model:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d8ece0)
body 🔸 V_Struct
body 🔸 V_Struct_ObservedObject
makeUIView(context:) 🔸 V_Struct_Representable
updateUIView(_:context:) 🔸 V_Struct_Representable
makeUIView(context:) 🔸 V_Struct_Representable_ObservedObject
updateUIView(_:context:) 🔸 V_Struct_Representable_ObservedObject
makeUIView(context:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600002d8ecc0)
updateUIView(_:context:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600002d8ecc0)
makeUIView(context:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d8ec40)
updateUIView(_:context:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d8ec40)
makeUIViewController(context:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600002d8ed00)
updateUIViewController(_:context:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600002d8ed00)
makeUIViewController(context:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d8ece0)
updateUIViewController(_:context:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d8ece0)

🟢 body ContentView 

init(model:) 🔸 V_Struct
init(model:) 🔸 V_Struct_ObservedObject
init(model:) 🔸 V_Struct_Representable
init(model:) 🔸 V_Struct_Representable_ObservedObject
init(model:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600002d94340)
init(model:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d94300)
init(model:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600002d94440)
init(model:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d943a0)
body 🔸 V_Struct_ObservedObject
updateUIView(_:context:) 🔸 V_Struct_Representable_ObservedObject
updateUIView(_:context:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600002d94340)
updateUIView(_:context:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d94300)
updateUIViewController(_:context:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600002d94440)
updateUIViewController(_:context:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d943a0)
deinit 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600002d8ecc0)
deinit 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d8ec40)
deinit 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600002d8ed00)
deinit 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d8ece0)

🟢 body ContentView 

init(model:) 🔸 V_Struct
init(model:) 🔸 V_Struct_ObservedObject
init(model:) 🔸 V_Struct_Representable
init(model:) 🔸 V_Struct_Representable_ObservedObject
init(model:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600002d94800)
init(model:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d94480)
init(model:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600002d948a0)
init(model:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d948c0)
body 🔸 V_Struct_ObservedObject
updateUIView(_:context:) 🔸 V_Struct_Representable_ObservedObject
updateUIView(_:context:) 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600002d94800)
updateUIView(_:context:) 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d94480)
updateUIViewController(_:context:) 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600002d948a0)
updateUIViewController(_:context:) 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d948c0)
deinit 🔹 V_Class_Representable 🔹 ObjectIdentifier(0x0000600002d94340)
deinit 🔹 V_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d94300)
deinit 🔹 VC_Class_Representable 🔹 ObjectIdentifier(0x0000600002d94440)
deinit 🔹 VC_Class_Representable_ObservedObject 🔹 ObjectIdentifier(0x0000600002d943a0)

*/