How to retrive data through database observer in Swift4 with couchbase?

Question

I am new to Couchbase as well as Nosql. I can upload data on CouchBase DB and retrieve them through enumerator and show them in a table view. But i want to retrieve data by observer which can observe a change on DB and i can save those data immediately in my local DB from Couchbase DB. I am on Swift4 Xcode9.1. Can anyone help me please???

Answer 1

By following database change can be observed in Swift4

NotificationCenter.default.addObserver(forName: NSNotification.Name.cblDatabaseChange, object: database, queue: nil) {
            (notification) -> Void in
            if let changes = notification.userInfo!["changes"] as? [CBLDatabaseChange] {
                for change in changes {
                    NSLog("Document '%@' changed.", change.documentID)
                    let document =  self.database.document(withID: change.documentID)
                    var properties = document?.properties
                    if let id = properties?["id"] as? String, let name = properties?["name"] as? String, let age = properties?["age"] as? String {

                        self.person.uniqueIDs = Int(id)
                    print(self.person.uniqueIDs ?? "i")
                    self.person.names = name
                    print(self.person.names ?? "n")
                    self.person.ages = Int(age)
                    print(self.person.ages ?? "a")

                    self.core.savedObjects(id: Int(self.person.uniqueIDs), name: String(self.person.names), age: Int(self.person.ages))
                    }
                }
            }
        }

Answer 2

Try to use this below method while getting data so it will detect changes in DB.

Make one function like below:

fileprivate func addLiveQueryObserverAndStartObserving() {
        guard let liveQuery = liveQuery else {
            return
        }

        // 1. iOS Specific. Add observer to the live Query object
        liveQuery.addObserver(self, forKeyPath: "rows", options: NSKeyValueObservingOptions.new, context: nil)

        // 2. Start observing changes
        liveQuery.start()

    }

Also refer this starterkit