title: Xcode SwiftUI window not shown after successful build
body: <p>I get the following warning, on <code>main.storyboard</code></p>
  <pre><code>Unsupported Configuartion:
  Window Controller requires a content view controller
  
  </code></pre>
  <p>This is the custom class linked to the <code>Window Controller</code>, which is also the <code>StoryBoard Entry Point</code>,</p>
  <pre><code>
  import Cocoa
  import SwiftUI
  
  class FirstWindowController: NSWindowController {
      
      override func windowDidLoad() {
          super.windowDidLoad()
          
          
          let contentView =  ContentView(myListModel: MyListModel())
              .environmentObject(UserData())
          
          
          self.window?.contentView = NSHostingView(rootView: contentView)
         
      }
     
  }
  
  </code></pre>
  <p>This is inside the <code>AppDelegate.swift</code> which is annotated as <code>@NSApplicationMain</code>.</p>
  <pre><code>func applicationDidFinishLaunching(_ aNotification: Notification) {
        
         window = NSWindow(
             contentRect: NSRect(x: 0, y: 0, width: 480, height: 300),
              styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
              backing: .buffered, defer: false)
          window.center()
          window.setFrameAutosaveName(&quot;Main Window”)
  
  }
  
  </code></pre>
  <p>The <code>main.storyboard</code>, <code>AppDelegate.swift</code>, and <code>FirstWindowController.swift</code> are identical to those of a project which was launching and showing the application window with no problem. I just renamed it to something else, and removed the <code>Core Data</code> support from the code. But in this project, the window doesn’t show up after successful build.</p>
  <p>I also have checked and compared all the configuration of the storyboard for both of these projects. They seem to be totally identical.</p>
  <p>Any help for fixing this would be appreciated.</p>