ios14 Xcode 12 - Sprites do not show when touching SwiftUI objects but work when touching SKScene

Question

I am working on a simple game to learn the new functionality of SwiftUI with SpriteKit in Xcode 12. When a user touches the SKScene touchesBegan() everything works as expected. When a user touches the Circle() gesture(DragGesture()) , I call the same function, but nothing shows. I can tell from the logs that the function showFragments(location:) is getting called, but nothing shows on screen. Any ideas?

Here is the code:

import SpriteKit
import SwiftUI


struct ContentView: View {
    
    var scene: GameScene {
        let scene = GameScene()
        scene.size = CGSize(width: 350, height: 600)
        scene.scaleMode = .fill
        scene.backgroundColor = .white
        return scene
    }
    var body: some View {
        ZStack {
            SpriteView(scene: scene)
                .frame(width: 350, height: 600)
                .edgesIgnoringSafeArea(.all)
            
            Circle()
                .fill(Color.blue)
                .frame(width: 50, height: 50)
                .gesture(
                    DragGesture(minimumDistance: 0.0)
                        .onChanged({ _ in
                            self.scene.showFragments(location: CGPoint(x: 150, y: 300))
                        })
                )
        }
    }
}

class GameScene: SKScene {
    override func didMove(to view: SKView) {
        physicsBody = SKPhysicsBody(edgeLoopFrom: frame)
    }
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        self.showFragments(location: CGPoint(x: 150, y: 300))
    }
    
    public func showFragments(location: CGPoint) {
        
        var i: Int = 0
        while i <= 3 {
            i += 1
            let fragment = SKSpriteNode(texture: SKTexture(imageNamed: "Brown Armor Fragment"))
            fragment.position = location
            print ("fragment \(i): \(fragment.position)")
            let wait = SKAction.wait(forDuration: 1)
            let remove = SKAction.run({() in fragment.removeFromParent() })
            
            
            fragment.physicsBody = SKPhysicsBody(texture: SKTexture(imageNamed: "Brown Armor Fragment"), alphaThreshold: 0.1, size: CGSize(width: 8, height: 6.5))
            self.addChild(fragment)
            let vx = Double.random(in: -1...1)
            fragment.physicsBody?.applyImpulse(CGVector(dx: vx, dy: 0))
            fragment.run(SKAction.sequence([wait, remove]))
        }
    }
}

Answer 1

You defined computable property for scene, so it creates different scene for circle gesture.

The solution is to use once-defined scene (tested with Xcode 12 / iOS 14). Use the following expression for scene:

struct ContentView: View {

    let scene: GameScene = {
        let scene = GameScene()
        scene.size = CGSize(width: 350, height: 600)
        scene.scaleMode = .fill
        scene.backgroundColor = .white
        return scene
    }()

    // ... other code

}