Programmatically created ARSCNView doesn't work

Question

I have created ARSCNView programmatically as the below code. The app runs on my real iPhone (without crashing) but shows a blank/black screen. It doesn't ask for accessing the camera either (I have the line "Privacy - Camera Usage Description" in Info.plist already). With the commented line sceneView.backgroundColor = .green I am sure the ARSCNView is created, added, and full screen.

import ARKit

class ViewController: UIViewController {
    let sceneView = ARSCNView()

    override func viewDidLoad() {
        super.viewDidLoad()
        sceneView.frame = self.view.frame
        self.view.addSubview(sceneView)
        // make sure the sceneView is added and full screen
        //sceneView.backgroundColor = .green
    }
}

Answer 1

You need to add SCNScene to your ARSCNView

let scene = SCNScene()
sceneView.scene = scene

And start ARWorldTrackingConfiguration in viewWillAppear

//Inside view will appear
let config = ARWorldTrackingConfiguration()
self.sceneView.session.run(config)