Identify which sprite node was hit - swift

Question

I would like to be able to identify which exact target sprite node is hit when the user flings another sprite at a group of target sprites. Here is how I set up my sprites under the didMoveToView function (only including the relevant lines of code here)
let flingerTexture = SKTexture(imageNamed: "flinger")
flingerNode.position = CGPoint(x: 768, y: 440)
flingerNode.physicsBody = SKPhysicsBody(texture: flingerTexture, size: flingerNode.size)
flingerNode.physicsBody?.dynamic = true
flingerNode.physicsBody!.categoryBitMask = PhysicsCategory.Flinger
flingerNode.physicsBody!.collisionBitMask = PhysicsCategory.Edge | PhysicsCategory.Bubble | PhysicsCategory.Ball
flingerNode.physicsBody?.contactTestBitMask = PhysicsCategory.Ball
let rotationConstraint = SKConstraint.zRotation(SKRange(lowerLimit: -π/4, upperLimit: π/4))
flingerNode.constraints = [rotationConstraint]
addChild(flingerNode)
// -------------Setup targets---------------
let range: Range<Int> = 1...10
for numbers in range {
let ballNode: BallNode = BallNode(imageNamed: "\(numbers)a")
let positionX = CGFloat.random(min: size.width / 6, max: size.width * 5/6)
let positionY = CGFloat.random(min: size.height * 4/9, max: size.height * 8/9)
ballNode.position = CGPoint(x: positionX, y: positionY)
ballNode.name = "Ball"
ballNode.ballIndex = Int(numbers)
index = ballNode.ballIndex
ballNode.ballHit = false
addChild(ballNode)
ballNode.physicsBody = SKPhysicsBody(circleOfRadius: 100)
ballNode.physicsBody!.affectedByGravity = false
ballNode.physicsBody?.dynamic = true
ballNode.physicsBody!.restitution = 0.5
ballNode.physicsBody!.friction = 0.0
ballNode.physicsBody!.categoryBitMask = PhysicsCategory.Ball
ballNode.physicsBody!.collisionBitMask = PhysicsCategory.Ball | PhysicsCategory.Bubble | PhysicsCategory.Edge | PhysicsCategory.Flinger | PhysicsCategory.Wall
ballNode.physicsBody?.contactTestBitMask = PhysicsCategory.Flinger
ballNode.userData = NSMutableDictionary()
ballArray.append(ballNode.ballIndex)
}
I am able to detect the collision, but am unable to retrieve the additional userData that would identify which exact ballNode was struck. When I tried the following code, it only returns an output of "nil".
func didBeginContact(contact: SKPhysicsContact!) {
let collision = contact.bodyA.categoryBitMask | contact.bodyB.categoryBitMask
if collision == PhysicsCategory.Flinger | PhysicsCategory.Ball {
println(ballNode.userData)
}
}

Answer 1

I am assuming that PhysicsCategory.Flinger is less than PhysicsCategory.Ball. Then in didContactBegan you can use this code.
func didBeginContact(contact: SKPhysicsContact) {
var body1 : SKPhysicsBody!
var body2 : SKPhysicsBody!
if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
body1 = contact.bodyA
body2 = contact.bodyB
}
else {
body1 = contact.bodyB
body2 = contact.bodyA
}
if body1.categoryBitMask == PhysicsCategory.Flinger &&
body2.categoryBitMask == PhysicsCategory.Ball {
if let ballNode = body2.node {
println(ballNode.userData)
}
}
}
The conditions have to be reversed if PhysicsCategory.Flinger is greater than PhysicsCategory.Ball.
if body1.categoryBitMask == PhysicsCategory.Ball &&
body2.categoryBitMask == PhysicsCategory.Flinger {
if let ballNode = body1.node {
println(ballNode.userData)
}
}

Answer 2

Thanks so much for pointing me in the right direction #rakeshbs! Your didBeginContact method works - the problem was I wasn't adding the userData correctly. I resolved this by adding the following line to my didMoveToView function:
ballNode.userData = ["ballNumber" : ballNode.ballIndex]