UIControlEvents

UIControlEvents are part of the UIKit framework used in iOS development to represent the various user interactions that can occur with UIControl objects, such as buttons, switches, sliders, and text fields. In Swift, UIControl.World UIControl.Event is an option set built around raw UInt values, allowing multiple events to be combined using the bitwise OR operator. In Objective‑C, the equivalent enumeration is UIControlEvents, defined as a typedef of NS_OPTIONS with values like UIControlEventTouchUpInside, UIControlEventValueChanged, and UIControlEventEditingChanged.

Typical events include:

• UIControlEventTouchDown – the user touches the control and it has not moved off its bounds.

• UIControlEventTouchUpInside – the user lifts a finger while still inside the control bounds, commonly used to trigger actions from buttons.

• UIControlEventTouchUpOutside – lift occurs outside the control bounds.

• UIControlEventValueChanged – state or value of the control changes, e.g., a UISlider adjusts its value.

• UIControlEventEditingChanged – used with text fields to detect live input changes.

• UIControlEventAllEvents – a catch‑all constant for testing or debugging.

To respond to an event, a target-action pair is registered with addTarget(_:action:for:) on the UIControl. The action method receives the control as a parameter, allowing it to inspect properties such as currentTitle or value. Multiple events can be bound to the same action or separate actions can be used.

Because UIControlEvents are option sets, developers can combine them for concise code, for example UIControlEventTouchUpInside | UIControlEventTouchUpOutside. In Swift 5, the typealias UIControl.Event is used directly while the legacy UIControlEvents constants remain available for backward compatibility. UIControlEvents provide a unified mechanism across all UIKit controls, simplifying event handling and enabling consistent user interface behavior.