Drop a dynamic square on a static rectangle

Roughly based on code in Jonathon Manning & Paris Buttfield-Addison's iOS Swift Game Development Cookbook. My full code below.

import SwiftUI
import SpriteKit

class GameScene: SKScene {
override func didMove(to view: SKView) {
let box = SKSpriteNode(color: .blue, size: CGSize(width: 100, height: 100))
box.position = CGPoint(x: UIScreen.main.bounds.width / 2,
y: UIScreen.main.bounds.height / 4 * 3)
box.physicsBody = SKPhysicsBody(rectangleOf: box.size)

box.physicsBody?.isDynamic = true

addChild(box)

let staticBarrier = SKSpriteNode(color: .yellow, size: CGSize(width: 200, height: 25))
staticBarrier.position = CGPoint(x: frame.midX, y: frame.midY - 100)
staticBarrier.physicsBody = SKPhysicsBody(rectangleOf: staticBarrier.size)
staticBarrier.physicsBody?.isDynamic = false

scene?.addChild(staticBarrier)
}
}

struct ContentView: View {
var scene: SKScene {
let scene = GameScene()
scene.size = CGSize(width: UIScreen.main.bounds.width,
height: UIScreen.main.bounds.height)
scene.backgroundColor = .red

return scene
}

var body: some View {
SpriteView(scene: scene)
.ignoresSafeArea()
}
}

struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}