What are the main global variables and states in your application?

In iOS applications, the main global variables and states are usually related to managing the application's lifecycle and general settings:

• AppDelegate and SceneDelegate — contain the application's state, handle launch events, transition to background, etc.
• UserDefaults — a storage for settings and small data, accessible globally within the app.
• Singleton objects — classes implemented as singletons, often used to store global state, such as session managers, user settings, data caches.
• NotificationCenter — a mechanism for transmitting events and updating state between different parts of the app.
• Global constants and configurations — usually declared in separate files and accessible throughout the app.

Example of a singleton for storing global user state:

class UserManager {
    static let shared = UserManager()
    private init() {}

    var currentUser: User?
}

// Usage:
UserManager.shared.currentUser = someUser