d

src/App.swift

@@ -12,7 +12,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate
         window = UIWindow(frame: UIScreen.main.bounds)
         let vc = UIViewController()
         addSwiftUIViewAsChild(swiftUIView: V(), parent: vc.view)
-        vc.view.backgroundColor = .gray
+        vc.view.backgroundColor = .white
         window?.rootViewController = vc
         window?.backgroundColor = UIColor.white
         window?.makeKeyAndVisible()

src/MeetupId.yml

@@ -0,0 +1,6 @@
+version: 2
+
+model:
+  textApp: [String, ""]
+  textUI: [String, ""]
+

src/V.swift

@@ -13,7 +13,14 @@ struct V: View {
 
       TextField("Binding-3", value: $vm.text, formatter: TextFieldValueOwner())
         .padding(8)
-        .border(Color.green, width: 4)
+        .border(Color.blue, width: 2)
+
+      Button(action: vm.join.send) {
+        Text("Join")
+          .padding(8)
+          .border(vm.isJoinAvailable ? Color.green : Color.red, width: 4)
+      }
+
     }
     .frame(width: 320)
     .padding()

src/VM.swift

@@ -8,6 +8,8 @@ final class VM: ObservableObject {
     MeetupId.K.meetupIdTextApp.rawValue,
     MeetupId.onlyFormat
   )
+  var isJoinAvailable = true
+  let join = PassthroughSubject<Void, Never>()
   var subscriptions = [AnyCancellable]()
 
   init() {