UIAlertController

UIAlertController is a class in Apple's UIKit framework used to present alerts and action sheets to the user. It serves as a modern replacement for the older UIAlertView and UIActionSheet classes. UIAlertController provides a consistent and customizable way to display messages and gather input from the user.

There are two primary styles of alert controllers: alert and action sheet. An alert style typically appears in the center of the screen and is used for critical messages or actions requiring immediate user attention. An action sheet style slides up from the bottom of the screen and is often used for presenting a list of related actions.

UIAlertController allows for the addition of actions, which are represented by UIAlertAction objects. These actions are displayed as buttons within the alert or action sheet. Each UIAlertAction can have a title, a style (default, cancel, or destructive), and a handler block that is executed when the action is selected.

In addition to actions, UIAlertController can also present text fields for user input when using the alert style. Multiple text fields can be added to an alert, and their content can be accessed in the action handler.

Presenting a UIAlertController is done by calling the present(_:animated:completion:) method on a UIViewController. The completion handler is an optional block that is executed after the presentation animation finishes. This class is a fundamental tool for user interaction within iOS applications.