NSUserUnixTask ignores script quietly - swift

Question

I'm writing a sandboxed app in Swift 4 on macOS High Sierra using Xcode 9. My app has a shell script file (say, myscript) copied to the Bundle.main.resourceURL directory when installing. I want to run this shell script using NSUserUnixTask as follows:
if let scriptUrl = URL(string: "myscript", relativeTo: Bundle.main.resourceURL) {
do {
let task = try NSUserUnixTask(url: scriptUrl)
task.execute(withArguments: [ "hello" ])
debugPrint("OK")
} catch let error {
debugPrint(error)
}
} else {
debugPrint("Script not found")
}
// output: "OK"
This gives no error messages and "OK" is correctly displayed. But the myscript script seems to be completely ignored. When I run myscript from Terminal instead, it runs as intended.
The test myscript file looks like:
#!/bin/sh
/usr/bin/osascript -e "tell app \"System Events\" to display dialog \"Message: $1\""
(The is only a test script; the real one calls emacsclient.) The shell script file is set executable (permission 755). Not only this shell script but also any other shell script seems ignored. For example, if the second line is replaced with /usr/bin/printf "\a", it does not beep. I tried many other shell scripts but nothing seems to work.
How can I solve this issue?
EDIT:
I was hasty. The class document says "If the application is sandboxed, then the script must be in the applicationScriptsDirectory folder." Now I want to know how to copy the script file upon installation.
EDIT 2:
I manually copied myscript to ~/Library/Applications Scripts/com.mydomain.myApp/ and then changed the first line of the above Swift codes (if let scriptUrl ...) to
let scriptFolderUrl = try! FileManager.default.url(for: .applicationScriptsDirectory,
in: .userDomainMask, appropriateFor: nil, create: true)
if let scriptUrl = URL(string: "myscript", relativeTo: scriptFolderURL) {
https://tutel.me/c/programming/questions/43741325/swift+3++sandbox++how+to+create+applicationscriptsdirectory+if+it+doesn39t+exist
The script runs. Now I need to figure out how to copy the script to the scripts folder when installing or running the app the first time.

Answer 1

pkamp requested a proper answer. :)
As the class document says, the script must be in the applicationScriptsDirectory folder. This folder is not writable by a sandboxed application, as vadian pointed out. The script (myscript) must be copied manually to the applicationScriptDirectory folder (e.g., ~/Library/Applications Scripts/com.mydomain.myApp/).
After this done, change the first line to the following:
// --------------------------------------------------------
let scriptFolderUrl = try! FileManager.default.url(for: .applicationScriptsDirectory,
in: .userDomainMask, appropriateFor: nil, create: true)
if let scriptUrl = URL(string: "myscript", relativeTo: scriptFolderURL) {
// --------------------------------------------------------
// same below
do {
let task = try NSUserUnixTask(url: scriptUrl)
task.execute(withArguments: [ "hello" ])
debugPrint("OK")
} catch let error {
debugPrint(error)
}
} else {
debugPrint("Script not found")
}
I benefited from this link for the first line.