.swift

 private func setupObservers() {
      
        self.rootRef.child("cloud-anchors").observe(.value) { (snapshot) in
         
            if let dictionary = snapshot.value as? [String:Any] {
                
                self.cloudIdentifier = dictionary["cloudIdentifier"] as! String
                let hex = dictionary["hex"] as! String
                
                if let cloudAnchor = try? self.gSession.resolveCloudAnchor(withIdentifier: self.cloudIdentifier) {
                    
                    let box = SCNBox(width: 0.3, height: 0.3, length: 0.3, chamferRadius: 0)
                    let material = SCNMaterial()
                    material.diffuse.contents = UIColor(fromHexString: hex)
                    box.materials = [material]
                    
                    let node = SCNNode(geometry: box)
                    node.position = SCNVector3(cloudAnchor.transform.columns.3.x, cloudAnchor.transform.columns.3.y, cloudAnchor.transform.columns.3.z)
                    self.sceneView.scene.rootNode.addChildNode(node)
                    
                }
            }
            
        }
    }