How to detect switch between macOS default & dark mode using Swift 3

I'm using this Swift 3 syntax successfully:

DistributedNotificationCenter.default.addObserver(self, selector: #selector(interfaceModeChanged(sender:)), name: NSNotification.Name(rawValue: "AppleInterfaceThemeChangedNotification"), object: nil)

func interfaceModeChanged(sender: NSNotification) {
  ...
}

Swift 5, Xcode 10.2.1, macOS 10.14.4

Great stuff. My two cents around @Jeffrey's answer:

extension Notification.Name {
    static let AppleInterfaceThemeChangedNotification = Notification.Name("AppleInterfaceThemeChangedNotification")
}

So one could (instead of rawValue):

func listenToInterfaceChangesNotification() {
    DistributedNotificationCenter.default.addObserver(
        self,
        selector: #selector(interfaceModeChanged),
        name: .AppleInterfaceThemeChangedNotification,
        object: nil
    )
}

Remember the @objc attribute:

@objc func interfaceModeChanged() {
    // Do stuff.
}