iOS Simulator showing Blank White Screen When Trying to Create Frame

In Chapter 4 of the Big Nerd Ranch: iOS Programming 4th Edition textbook where we're supposed to create a red rectangle appear in the middle of the view in the AppDelegate.m file and have it appear in the simulator.

I've copied the code word for word and when I run the simulator I get a blank screen like this:

I'm not sure why this is happening. I've already put the property for window in the AppDelegate.h file so I know that's not why.

This is the code in the AppDelegate.m file:

//
//  AppDelegate.m
//  Hypnosister
//
//
//

#import "AppDelegate.h"
#import "BNRHypnosisView.h"

@interface AppDelegate ()

@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    CGRect firstFrame = CGRectMake(160, 240, 100, 150);
    
    BNRHypnosisView *firstView = [[BNRHypnosisView alloc]initWithFrame:firstFrame];
    firstView.backgroundColor = [UIColor redColor];
    [self.window addSubview:firstView];
    
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    return YES;
}


#pragma mark - UISceneSession lifecycle


- (UISceneConfiguration *)application:(UIApplication *)application configurationForConnectingSceneSession:(UISceneSession *)connectingSceneSession options:(UISceneConnectionOptions *)options {
    // Called when a new scene session is being created.
    // Use this method to select a configuration to create the new scene with.
    return [[UISceneConfiguration alloc] initWithName:@"Default Configuration" sessionRole:connectingSceneSession.role];
}


- (void)application:(UIApplication *)application didDiscardSceneSessions:(NSSet<UISceneSession *> *)sceneSessions {
    // Called when the user discards a scene session.
    // If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
    // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
}


@end

If you use an application scene, the window you create manually in the application delegate is ignored (to be precise it remains the key window for very short period of time, until the scene makes its own window the key one). So you either should attach the window you created in the scene delegate's -[UISceneDelegate scene:willConnectToSession:options:] method:

- (void)scene:(UIScene *)scene willConnectToSession:(UISceneSession *)session options:(UISceneConnectionOptions *)connectionOptions {
    UIWindow *window = [[UIWindow alloc] initWithWindowScene:(UIWindowScene *)scene];

    UIView *view = [[UIView alloc] initWithFrame:CGRectMake(160, 240, 100, 150)];
    view.backgroundColor = UIColor.redColor;
    [window addSubview:view];

    window.backgroundColor = UIColor.whiteColor;
    [window makeKeyAndVisible];
    self.window = window;
}

..OR get rid of the scene delegate in your application (you may refer to the discussion under this question for more details on how to do it) and make it work with the old good application delegate's window. Be advised that in this case you won't be able to use the window without having the rootViewController specified, so you at least need to set a dummy controller:

_window.rootViewController = [UIViewController new];