ARSCNViewDelegate.swift

class ViewController: UIViewController, ARSCNViewDelegate {
    
    // Rest of class code goes above here ...
    
    func session(_ session: ARSession, cameraDidChangeTrackingState camera: ARCamera) {
        var status = "Loading..."
        switch camera.trackingState {
        case .notAvailable:
            status = "Not available"
        case .limited(_):
            status = "Analyzing..."
        case .normal:
            status = "Ready"
        }
        infoLabel.text = status
    }
}