applyImpulse not working when touching node - ios

Question

I have a circle on the screen that will slowly get bigger (incidentally, Balloon class is a type of SKShapeNode). In touchesBegan I click on the circle and it prints that I touched it, however no impulse is applied. How can I find the issue? I'm fairly new to SpriteKit.
import SpriteKit
import GameplayKit
class GameScene: SKScene {
var radius = 40.0
var balloon : Balloon? = nil
override func didMove(to view: SKView) {
balloon = Balloon(radius: radius, position: CGPoint(x: frame.midX, y: frame.minY + 250))
balloon?.name = "balloon"
let physicsBody = SKPhysicsBody(circleOfRadius: CGFloat(radius))
physicsBody.affectedByGravity = false
balloon?.physicsBody = physicsBody
balloon?.physicsBody?.isDynamic = true
let borderBody = SKPhysicsBody(edgeLoopFrom: self.frame)
borderBody.friction = 0
self.physicsBody = borderBody
physicsWorld.gravity = CGVector(dx: 0.0, dy: 0.0)
self.addChild(balloon!)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches {
let location = touch.location(in: self)
let node : SKNode = self.atPoint(location)
if node.name == "balloon" {
print("touching balloon.")
balloon?.physicsBody?.applyImpulse(CGVector(dx: 10.0, dy: 10.0), at: location)
}
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
}
override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
}
override func update(_ currentTime: TimeInterval) {
// Called before each frame is rendered
radius += 0.05
self.balloon?.radius = radius
let physicsBody = SKPhysicsBody(circleOfRadius: CGFloat(radius))
physicsBody.affectedByGravity = false
balloon?.physicsBody = physicsBody
balloon?.physicsBody?.isDynamic = true
}
}

Answer 1

You are creating a new body every update. If you want to inflate your balloon, use scale:
var scale = 1.0
override func update(_ currentTime: TimeInterval) {
// Called before each frame is rendered
scale += 0.05
self.balloon?.setScale(scale)
}
Then your physics body will be able to have the impulse applied to it because you won't be creating a new body each update.

Answer 2

The following line:
let location = touch.location(in: self)
finds the location of the touch in the scene. However, in the function call applyImpulse, it is relative to the node. Instead of
balloon?.physicsBody?.applyImpulse(CGVector(dx: 10.0, dy: 10.0), at: location)
use:
balloon?.physicsBody?.applyImpulse(CGVector(dx: 10.0, dy: 10.0), at: touch.location(in: balloon))