Calling AppleScript from Swift App, passing a parameter. Swift 3 version.

gistfile1.txt

// updated for Swift 3
import Carbon

// Swift version of https://developer.apple.com/library/mac/technotes/tn2084/_index.html

	@IBAction func testButtonPushed(sender: AnyObject) {
		
		guard let url = NSBundle.main.url(forResource: "SendFinderMessage", withExtension: "scpt") else {
			return
		}
		
		var errors: NSDictionary?
		guard let script = NSAppleScript(contentsOf: url, error: &errors) else {
			return
		}
		
		let message = NSAppleEventDescriptor(string: "Message from App")
		
		let parameters = NSAppleEventDescriptor.init(listDescriptor: ())
		parameters.insert(message, at: 1)
		
		var psn = ProcessSerialNumber(highLongOfPSN: UInt32(0), lowLongOfPSN: UInt32(kCurrentProcess))

		let target = NSAppleEventDescriptor(descriptorType: typeProcessSerialNumber, bytes:&psn, length:MemoryLayout<ProcessSerialNumber>.size)
		
		let handler = NSAppleEventDescriptor(string: "show_message")
		
		let event = NSAppleEventDescriptor.appleEventWithEventClass(AEEventClass(kASAppleScriptSuite), eventID: AEEventID(kASSubroutineEvent), targetDescriptor: target, returnID: AEReturnID(kAutoGenerateReturnID), transactionID: AETransactionID(kAnyTransactionID))
		
		event.setParam(handler, forKeyword: AEKeyword(keyASSubroutineName))
		event.setParam(parameters, forKeyword: AEKeyword(keyDirectObject))
		
		
		// ObjC version compares this to nil, but it is non optional!
		let descriptor = script.executeAppleEvent(event, error: &errors)
	}