The UIApplicationDelegate class.
The UIApplication.
Gets or sets the orientation of the application. Available values: "portrait", "landscape", "unknown".
The root view controller for the application.
Gets the system appearance. Available values: "dark", "light", null. Null for iOS <= 11.
The key window.
Adds an observer to the default notification center for the specified notification. For more information, please visit 'https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSNotificationCenter_Class/#//apple_ref/occ/instm/NSNotificationCenter/addObserver:selector:name:object:'
A string containing the name of the notification.
A callback function that will be called each time the observer receives a notification.
Removes the observer for the specified notification from the default notification center. For more information, please visit 'https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSNotificationCenter_Class/#//apple_ref/occ/instm/NSNotificationCenter/addObserver:selector:name:object:'
The observer that was returned from the addNotificationObserver method.
A string containing the name of the notification.
The abstraction of an iOS-specific application object.