ARKit Plane Detection - Value of type 'ARView' has no member 'session'

Question

I am trying to add plane detection to a simple ARKit app. I want to put a picture on a vertical plane.

So first I need to detect the plane then I can add my object anchor which I created in RealityKit.

However the problem is I am not sure the right method in detecting a plane and adding it to my scene with ARKit 3 and Xcode 11.

It should be as simple as:

import ARKit
import RealityKit

@IBOutlet var arView: ARView!

override func viewDidLoad() {
    super.viewDidLoad()

    let arConfiguration = ARWorldTrackingConfiguration()
    arConfiguration.planeDetection = .horizontal
    arView.session.run(arConfiguration)
} 

But I get the following error:

Value of type 'ARView' has no member 'session'

I even tried the following which was used as an example by Apple from their WWDC demo (4:27),

Apple Demo!

let anchor = AnchorEntity(plane: .verticle, minimumBounds: [0.2, 0.2])
arView.scene.addAnchor(anchor)

but I get the following error when trying to create an AnchorEntity

Expression type 'AnchorEntity' is ambiguous without more context

import UIKit
import RealityKit
import ARKit

class ViewController: UIViewController {

    @IBOutlet var arView: ARView!

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        // Create a session configuration
    }

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    func addFrame() {
        // Load the "Box" scene from the "Experience" Reality File
        let boxAnchor = try! Experience.loadBox()

        // Add the box anchor to the scene
        arView.scene.anchors.append(boxAnchor)
    }
}

Answer 1

You get this error if your build destination is set to a Simulator. You need to select either an Actual Device or Generic iOS Device.

I've banged my head on this a couple of time and now add the following comment

    // If the following line fails to compile "Value of type 'ARView' has no member 'session'"
    // You need to select a Real Device or Generic iOS Device and not a simulator
    arView.session.run(configuration)

Answer 2

If you use iOS Simulator for AR app based on Interface Builder Storyboard or if you use iOS SwiftUI Preview – then you can't implement session-oriented properties and anchoring components for ARView. As you can see there are a lot of errors in this case.

When Simulator is chosen in Xcode Active Scheme.

The only way to use session-oriented properties for your AR app is to choose a real iOS or iPadOS device in the Xcode Active Scheme drop-down menu.

When real Apple device is chosen for build.

The same is true for installGestures() method

iOS Simulator:

Real Device:

Answer 3

I managed to eliminate this problem by using conditional compilation.

#if !targetEnvironment(simulator)
    return ARView(frame: .zero)
#else
    return UIView(frame: .zero)
#endif

The compilation issues stopped, but I will admit that I still have problems with previews. But I think that is more related to code complexity than to this error.