// Create or open a database
  let database: Database
  do {
     database = try Database(name: "mydb")
  } catch {
     fatalError("Error opening database")
  }
  
  // Create a new document (i.e. a record) in the database.
  let mutableDoc = MutableDocument()
     .setFloat(2.0, forKey: "version")
     .setString("SDK", forKey: "type")
  
  // Save it to the database.
  do {
     try database.saveDocument(mutableDoc)
  } catch {
     fatalError("Error saving document")
  }
  
  // Update a document.
  if let mutableDoc = database
                      .document(withID: mutableDoc.id)
                      ?.toMutable() {
     mutableDoc.setString("Swift", forKey: "language")
     do {
         try database.saveDocument(mutableDoc)
         let document = database.document(withID: mutableDoc.id)!
     } catch {
         fatalError("Error updating document")
     }
  }
  
  // Create a query to fetch documents of type SDK.
  let query = QueryBuilder
     .select(SelectResult.all())
     .from(DataSource.database(database))
    .where(Expression.property("type").equalTo(Expression.string("SDK")))
  
  // Run the query.
  do {
     let result = try query.execute()
     print("Number of rows :: \(result.allResults().count)")
  } catch {
     fatalError("Error running the query")
  }
  
  // Create replicators to push and pull changes to and from the cloud.
  let targetEndpoint = 
    URLEndpoint(url: URL(string: "ws://localhost:4984/getting-started-db")!)
  var replConfig = ReplicatorConfiguration(database: database, target: targetEndpoint)
  replConfig.replicatorType = .pushAndPull
  
  // Add authentication.
  replConfig.authenticator = BasicAuthenticator(username: "john", password: "pass")
  
  // Create replicator 
  // (make sure to add an instance or static variable named replicator)
  let replicator = Replicator(config: replConfig)
  
  // Optionally,Listen to replicator change events.
  replicator.addChangeListener { (change) in
  if let error = change.status.error as NSError? {
         print("Error code :: \(error.code)")
       }
  }
  
  // Start replication.
  replicator.start()