"Expected end of line but found unknown token." while running AppleScript in swift

I am trying to run applescript code in swift to get information from other applications. Here is a sample code:

var applescript = "tell application "Xcode" \n set fileName to name of window 1 \n end tell"
var error: NSDictionary?
let scriptObject = NSAppleScript(source: applescript)
let output: NSAppleEventDescriptor = scriptObject!.executeAndReturnError(&error)
if (error != nil) {
    print("error: \(String(describing: error))")
}
if output.stringValue == nil{
    let empty = "the result is empty"
    return empty
}
else {
    return (output.stringValue?.description)!
}

But it always return me error messages like this:

error: Optional({
    NSAppleScriptErrorBriefMessage = "Expected end of line but found unknown token.";
    NSAppleScriptErrorMessage = "Expected end of line but found unknown token.";
    NSAppleScriptErrorNumber = "-2741";
    NSAppleScriptErrorRange = "NSRange: {25, 1}";
})

I think the unknown token it mentioned is "\n". Because when I ran other applescripts without "\n" in codes, there was no error message.

Can somebody help me this out? Thank you so much!

You have to escape the inner double quotes

let applescript = "tell application \"Xcode\" \n set fileName to name of window 1 \n end tell"

Or, more convenient and more legible with the multiline syntax

let applescript = """
    tell application "Xcode"
        set fileName to name of window 1
    end tell
"""