RealityKit-Entity-AddCollisions.swift

extension CustomEntity {
  func addCollisions() {
    guard let scene = self.scene else {
      return
    }

    collisionSubs.append(scene.subscribe(to: CollisionEvents.Began.self, on: self) { event in
        guard let boxA = event.entityA as? CustomEntity else {
        return
      }

    boxA.model?.materials = [SimpleMaterial(color: .red, isMetallic: false)]
    })
    collisionSubs.append(scene.subscribe(to: CollisionEvents.Ended.self, on: self) { event in
        guard let boxA = event.entityA as? CustomEntity else {
        return
      }
      boxA.model?.materials = [SimpleMaterial(color: .yellow, isMetallic: false)]
    })
  }
}