How to quit or close an app in macOS using Swift?

You can quit or exit an app with:

NSApp.terminate(self)

If you’re making a macOS menu bar app in Swift and have an option in the dropdown menu to quit the app then your code would look something like:

NSMenuItem(title: "Quit", action: #selector(quitClicked), keyEquivalent: "q")

Menu Bar Item

@objc private func quitClicked() {
    NSApp.terminate(self)
}

Function invoked when a user clicks on the menu item

Note: Do not forget to add @objc in front of the function so that it can be called from #selector.