Notification extensions in Swift 3

gistfile1.txt

NotificationCenter.default.post(identifier: .DidChangeSession, object: nil)

NotificationCenter.default.addObserver(
  self, selector: #selector(didChangeNoticeState(didChangeSession:)),
  identifier: .DidChangeSession, object: nil)

NotificationCenter.default.rx.notification(.didChangeSession)
  .subscribe(onNext: { [weak self] (_) in
  })

NotificationExtension.swift

extension Notification {
    // MARK: - Identifier
    enum Identifier: String {
        case DidChangeSession
    }


    // MARK: - UserInfoKey
    enum UserInfoKey: String {
        case Session
    }
}


///
/// MARK: - Notification.Name
///
extension Notification.Name {
    init(identifier: Notification.Identifier) {
        self.init(identifier.rawValue)
    }
}


///
/// MARK: - NotificationCenter
///
extension NotificationCenter {
    func addObserver(_ observer: Any, selector aSelector: Selector, identifier aIdentifier: Notification.Identifier, object anObject: Any?) {
        addObserver(observer, selector: aSelector, name: Notification.Name(identifier: aIdentifier), object: anObject)
    }

    func removeObserver(_ observer: Any, identifier aIdentifier: Notification.Identifier, object anObject: Any?) {
        removeObserver(observer, name: Notification.Name(identifier: aIdentifier), object: anObject)
    }

    func post(identifier aIdentifier: Notification.Identifier, object anObject: Any?, userInfo aUserInfo: [AnyHashable : Any]? = nil) {
        post(name: Notification.Name(identifier: aIdentifier), object: anObject, userInfo: aUserInfo)
    }
}


///
/// MARK: - Notification
///
extension Notification {
    func userInfoValue(forKey key: Notification.UserInfoKey) -> Any? {
        guard let userInfo = userInfo else { return nil }
        return userInfo[key.rawValue]
    }
}


///
/// MARK: - Rx
///
import RxSwift

extension Reactive where Base : NotificationCenter {
    /**
     Transforms notifications posted to notification center to observable sequence of notifications.

     - parameter aIdentifier: Optional identifier used to filter notifications.
     - parameter object: Optional object used to filter notifications.
     - returns: Observable sequence of posted notifications.
     */
    func notification(_ aIdentifier: Notification.Identifier, object: AnyObject? = nil) -> Observable<Notification> {
        return notification(Notification.Name(identifier: aIdentifier), object: object)
    }
}