Can you execute an Applescript script from a Swift Application

For anyone who is getting the warning below for Swift 4, for the line while creating an NSAppleEventDescriptor from zekel's answer

Non-optional expression of type 'NSAppleEventDescriptor' used in a check for optionals

You can get rid of it with this edited short version:

let myAppleScript = "..."
var error: NSDictionary?
if let scriptObject = NSAppleScript(source: myAppleScript) {
    if let outputString = scriptObject.executeAndReturnError(&error).stringValue {
        print(outputString)
    } else if (error != nil) {
        print("error: ", error!)
    }
}

However, you may have also realized; with this method, system logs this message to console everytime you run the script:

AppleEvents: received mach msg which wasn't complex type as expected in getMemoryReference.

Apparently it is a declared bug by an Apple staff developer, and is said to be 'just' a harmless log spam and is scheduled to be removed on future OS updates, as you can see in this very long apple developer forum post and SO question below:

AppleEvents: received mach msg which wasn't complex type as expected in getMemoryReference

Thanks Apple, for those bazillions of junk console logs thrown around.

As Kamaros suggests, you can call NSApplescript directly without having to launch a separate process via NSTask (as CRGreen suggests.)

Swift Code

let myAppleScript = "..."
var error: NSDictionary?
if let scriptObject = NSAppleScript(source: myAppleScript) {
    if let output: NSAppleEventDescriptor = scriptObject.executeAndReturnError(
                                                                       &error) {
        print(output.stringValue)
    } else if (error != nil) {
        print("error: \(error)")
    }
}

Tested: one can do something like this (arbitrary script path added):

import Foundation
 
let task = Process()
task.launchPath = "/usr/bin/osascript"
task.arguments = ["~/Desktop/testscript.scpt"]
 
task.launch()

You can try NSAppleScript, from Apple's Technical Note TN2084 Using AppleScript Scripts in Cocoa Applications https://developer.apple.com/library/mac/technotes/tn2084/_index.html

NSAppleScript* scriptObject = [[NSAppleScript alloc] initWithSource:
            @"\
            set app_path to path to me\n\
            tell application \"System Events\"\n\
            if \"AddLoginItem\" is not in (name of every login item) then\n\
            make login item at end with properties {hidden:false, path:app_path}\n\
            end if\n\
            end tell"];

returnDescriptor = [scriptObject executeAndReturnError: &errorDict];