Signals in ActionScript

Here’s the translation of the Go signals example to ActionScript, formatted in Markdown suitable for Hugo:

Our program demonstrates how to handle signals in ActionScript. Although ActionScript doesn’t have direct equivalents to Unix signals, we can simulate similar behavior using the NativeApplication class and its events.

package {
    import flash.desktop.NativeApplication;
    import flash.events.Event;
    import flash.events.InvokeEvent;
    import flash.display.Sprite;

    public class SignalHandler extends Sprite {
        public function SignalHandler() {
            NativeApplication.nativeApplication.addEventListener(Event.EXITING, onExiting);
            NativeApplication.nativeApplication.addEventListener(Event.ACTIVATE, onActivate);
            NativeApplication.nativeApplication.addEventListener(Event.DEACTIVATE, onDeactivate);

            trace("Awaiting application events...");
        }

        private function onExiting(event:Event):void {
            trace("\nApplication is exiting");
            // Perform cleanup or save state here
            trace("Exiting");
        }

        private function onActivate(event:Event):void {
            trace("\nApplication activated");
        }

        private function onDeactivate(event:Event):void {
            trace("\nApplication deactivated");
        }
    }
}

In this ActionScript example, we’re using the NativeApplication class to listen for application-level events that are somewhat analogous to system signals:

1. We create event listeners for EXITING, ACTIVATE, and DEACTIVATE events.

2. The onExiting function is called when the application is about to exit. This is similar to handling a SIGTERM signal in Unix systems.

3. The onActivate and onDeactivate functions are called when the application gains or loses focus, respectively. While not direct equivalents to Unix signals, they demonstrate how to respond to system-level events.

4. We use trace to output messages to the console, which is ActionScript’s equivalent of fmt.Println.

To run this program:

1. Save the code in a file named SignalHandler.as.
2. Compile it using the ActionScript compiler (part of the Flex SDK).
3. Run the resulting SWF file in a Flash player or AIR runtime.

When you run the application, it will wait for events. Depending on your environment:

• Closing the application window will trigger the EXITING event.
• Switching to and from the application will trigger ACTIVATE and DEACTIVATE events.

This example demonstrates how to handle application-level events in ActionScript, which is the closest equivalent to signal handling in desktop or mobile AIR applications.