Type safe NotificationCenter

NotificationCenter+TypeSafe.swift

struct Notification<T> {
    let name: NSNotification.Name
}

private let notificationData = "_notificationData"

extension NotificationCenter {
    func post<T>(_ notification: Notification<T>, object: Any? = nil, data: T) {
        post(name: notification.name, object: object, userInfo: [notificationData: data])
    }
    func addObserver<T>(for notification: Notification<T>, object obj: Any? = nil, queue: OperationQueue? = .main, using block: @escaping (T) -> Void) -> NSObjectProtocol {
        return addObserver(forName: notification.name, object: obj, queue: queue) { n in
            block(n.userInfo![notificationData] as! T)
        }
    }
}

Usage.swift

enum Foo {
    case int(Int)
    case str(String)
}

extension Notification {
    static var foo: Notification<Foo> { return .init(name: .init(#function)) }
}

let x = NotificationCenter.default.addObserver(for: .foo) { foo in
    print(foo)
}

NotificationCenter.default.post(.foo, data: .int(1))
NotificationCenter.default.post(.foo, data: .str("wooo"))
NotificationCenter.default.post(.foo, data: .int(42))