How to display NSSavePanel in MacOS?

I'm trying to show NSSavePanel (or any "Save File Dialog") on Mac OSX. I'm building COCOA application in XCode Version 9.3 (9E145) in Swift 4 (or 4.2? I'm not sure exactly).

I've tried everything...

Like this?

    let savePanel = NSSavePanel()
    savePanel.begin { (result) in
        if result.rawValue == NSApplication.ModalResponse.OK.rawValue {


        }
    }

this?

    let savePanel = NSSavePanel()
    savePanel.canCreateDirectories = true
    savePanel.showsTagField = false
    savePanel.nameFieldStringValue = "result.csv"
    savePanel.level = NSWindow.Level(rawValue: Int(CGWindowLevelForKey(.modalPanelWindow)))
    savePanel.begin { (result) in
        if result.rawValue == NSApplication.ModalResponse.OK.rawValue {


        }
    }

many many other ways...

What am I missing? Thanks!