Notifier_ExampleCode.swift

extension Selector {
    static let coffeeMadeNotification = #selector(Customer.drink(_:))
}

class Customer {
    @objc func drink(notification: NSNotification) {
        print("Mmm... Coffee")
    }
}

let customer = Customer()

Barista.addObserver(customer, selector: .coffeeMadeNotification, notification: .coffeeMade)

Barista.postNotification(.coffeeMade)
// prints: Mmm... Coffee

Barista.removeObserver(customer, notification: .coffeeMade)