Change image when collision is detected in swift

I need to change the image of the enemy SKSpriteNode when the player collides, but in the game I will have many enemies and I want change only the selected.

Enemy.name is the number of lives, i don't now if a can do this differently

func setupPlayer(){
    player = SKSpriteNode(imageNamed: "ball")
    player.anchorPoint = CGPoint(x: 0.5, y: 0.5)
    player.position = CGPoint(x: size.width/2, y: 60)
    player.zPosition = Layer.Player.rawValue
    player.physicsBody = SKPhysicsBody(circleOfRadius: player.size.width / 2)
    player.physicsBody?.mass = 1
    player.physicsBody?.restitution = 0.7
    player.physicsBody?.dynamic = true
    player.physicsBody?.categoryBitMask = playerCategory
    player.physicsBody?.contactTestBitMask = enemyCategory 
    worlNode.addChild(player)
    nuevoPlayerControl = true
}

func setupEnemy(){
    if nuevoPlayerControl == true && nuevoPlayer == true{
        enemy = SKSpriteNode(imageNamed: "ball")
        enemy.anchorPoint = CGPoint(x: 0.5, y: 0.5)
        enemy.zPosition = Layer.Player.rawValue
        enemy.position = CGPoint(x: 250, y: 300)
        enemy.physicsBody?.mass = 1
        enemy.zRotation = player.zRotation
        enemy.size = player.size
        enemy.physicsBody = SKPhysicsBody(circleOfRadius: enemy.size.width/2)
        enemy.physicsBody?.friction = 1
        enemy.physicsBody?.dynamic = true
        enemy.physicsBody?.categoryBitMask = enemyCategory
        enemy.physicsBody?.contactTestBitMask = playerCategory 
        enemy.name = "3"
        worlNode.addChild(enemy)
    }
}

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 == playerCategory && body2.categoryBitMask == enemyCategory {
        //here the enemy lose a live and the image should change
        let lives = body2.node?.name
        if lives! == "3" {
            body2.node?.name = "2"
        }
        if lives! == "2" {
            body2.node?.name = "1"
        }
        if lives! == "1" {
            body2.node?.removeFromParent()
        }
        print(lives)
    }
 }