Notifications.swift

protocol NotificationType {
    var name: Notification.Name { get }
    static var name: Notification.Name { get }
    var userInfo: [AnyHashable : Any] { get }
    
    init?(notification: Notification?)
}

struct Notifications { }

extension NotificationCenter {
    func post(_ notification: NotificationType, object: Any? = nil) {
        post(name: notification.name, object: object, userInfo: notification.userInfo)
    }
    
    func addObserver<T:NotificationType>(forType type: T.Type, object obj: Any? = nil, queue: OperationQueue? = nil, using block: @escaping (T?) -> Swift.Void) -> NSObjectProtocol {
        return addObserver(forName: type.name, object: obj, queue: queue) { block( type.init(notification: $0) ) }
    }
}

extension Notifications {
    struct openUserProfile: NotificationType {
        var userId:String
        
        static var name: Notification.Name {
            return Notification.Name("LP_openUserProfile")
        }
        
        var name:Notification.Name {
            return openUserProfile.name
        }
        
        var userInfo: [AnyHashable : Any] {
            return [ "userId" : userId]
        }
        
        init(userId: String) {
            self.userId = userId
        }
        
        init?(notification: Notification?) {
            guard
                let name = notification?.name,
                let userId = notification?.userInfo?["userId"] as? String,
                name == openUserProfile.name
                else { return nil }
            
            self.userId = userId
        }
    }
}