How can a View be attached to a window in an application?

In iOS, to attach a UIView to the application window, you typically use the window property of the scene or the application, as well as the view hierarchy. The main method is to add your UIView as a subview to the window's root view controller or directly to the window itself.

Example:

if let window = UIApplication.shared.windows.first {
    let myView = UIView(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
    myView.backgroundColor = .red
    window.addSubview(myView)
}

You can also work through UIWindowScene and its windows in modern multi-scene applications.

It is important to remember that views are usually added to view controllers, not directly to the window, to properly handle the lifecycle and auto layout.