ThreadSafeReferenceDecoder.swift

    var connectionRef: ThreadSafeReference<NetworkConnection>? = nil
    
    var connection: NetworkConnection? {
        get {
            guard let ref = self.connectionRef else {
                return nil
            }
            self.mutex.lock()
            defer {
                self.mutex.unlock()
            }
            
            let realm = try! Realm()
            guard let conection = realm.resolve(ref) else {
                return nil // person was deleted
            }
            self.connectionRef = ThreadSafeReference(to: conection)
            return conection
        }
        set {

            self.mutex.lock()
            defer {
                self.mutex.unlock()
            }
            guard let value = newValue else {
                self.connectionRef = nil
                return
            }
            self.connectionRef = ThreadSafeReference(to: value)
        }
    }