Collision detection on SpriteKit of two objects

I am having trouble detecting a collision of two objects when I fire my cannon. The goal is to fire a bullet out of it and remove as soon as it cools down with an obstacle. There seems to be no collision in the game as I cannot get the "Collision" message I have set. Take a look at the following code:

class GameScene: SKScene, SKPhysicsContactDelegate {


enum BodyType: UInt32 {
    case bullet = 1
    case line = 2
    case breaker = 4
}

      

        
        
        
      

    

I have listed the components, so I can install them in the Bitmask category. After that I made the setting when shooting when the touch starts.

 override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {

    /* Called when a touch begins */

    for touch in (touches as! Set<UITouch>) {

    let bullet = SKSpriteNode(imageNamed: "bullet.png")

    bullet.position = self.shooterTriangle.position

    var actionRotate = SKAction.rotateToAngle(CGFloat(2 * -M_PI), duration: NSTimeInterval(0.1))

    let actionMove = SKAction.moveTo(CGPoint(x: 500, y: size.height * 0.5), duration: NSTimeInterval(0.5))

    let removeBullet = SKAction.removeFromParent()

    bullet.runAction(SKAction.sequence([actionRotate]))

    bullet.runAction(SKAction.sequence([actionMove, removeBullet]))

    addChild(bullet)

        // Bullet Physics Start ****

        bullet.physicsBody? = SKPhysicsBody(circleOfRadius: bullet.size.width/2.0)

        bullet.physicsBody?.dynamic = true
        bullet.physicsBody?.affectedByGravity = false
        bullet.physicsBody?.allowsRotation = false
        bullet.physicsBody?.categoryBitMask = BodyType.bullet.rawValue
        bullet.physicsBody?.contactTestBitMask = BodyType.line.rawValue
        bullet.physicsBody?.collisionBitMask = BodyType.line.rawValue

    }
}

      

        
        
        
      

    

Then I'll add the line, I want the bullet to match the loadGameComponents function ...

func loadGameComponents() {

//Load line....

    let line = SKSpriteNode(imageNamed: "Line_1.png")

    line.position = CGPoint(x: size.width * 0.95, y: size.height * (2.0))

    addChild(line)

    var actualSpeedDuration = 2.2

    let lineActionMove = SKAction.moveTo(CGPoint(x: size.width * 0.95, y: size.height * 0.6), duration: NSTimeInterval(actualSpeedDuration))

    line.runAction(SKAction.sequence([lineActionMove]))

    // Line Physics starts! *****

    line.physicsBody? = SKPhysicsBody(rectangleOfSize: CGSize(width: line.size.width, height: line.size.height))

    line.physicsBody?.dynamic = false
    line.physicsBody?.affectedByGravity = false
    line.physicsBody?.allowsRotation = false
    line.physicsBody?.categoryBitMask = BodyType.line.rawValue
    line.physicsBody?.contactTestBitMask = BodyType.bullet.rawValue
    line.physicsBody?.collisionBitMask = 0

      

        
        
        
      

    

Finally, I defined contactDelegate = self in my didLoad function and included didBeginContact method

func didBeginContact(contact: SKPhysicsContact) {
    println("Contact!!!")
}

      

        
        
        
      

    

I don't get the message at all, but I'm not sure what is going wrong!

Thank you for your patience!:)