Random Duration in SKAction in Swift - swift

Question

How can I random those two objects’ duration?
func start() {
let ajusdtedDuration = NSTimeInterval (frame.size.width / kDefaultXToMovePerSecond)
let moveLeft = SKAction.moveByX(-frame.size.width/2, y: 0, duration: ajusdtedDuration/2)
let resetPosition = SKAction.moveToX(0, duration: 0)
let moveSequence = SKAction.sequence([moveLeft, resetPosition])
runAction(SKAction.repeatActionForever(moveSequence))
}
func stop() {
removeAllActions()
}
And this is another one. Plus, how can I make both of their duration synced?
func startMoving() {
let moveLeft = SKAction.moveByX(-kDefaultXToMovePerSecond, y: 0, duration: 1)
runAction(SKAction.repeatActionForever(moveLeft))
}

Answer 1

You can create a random number and use it for your duration.
The function could look like that:
func randomBetweenNumbers(firstNum: CGFloat, secondNum: CGFloat) -> CGFloat{
return CGFloat(arc4random()) / CGFloat(UINT32_MAX) * abs(firstNum - secondNum) + min(firstNum, secondNum)
}
To sync both actions, you don't need to do much. Because if you call actions after each other, they will be started at the same time. Just call the function once and use it for both of your functions:
//Number between 0 and 10
let randomTime = randomBetweenNumbers(0, secondNum: 10)
Then you use it. The best way would be to use it as a parameter in your functions:
func startMoving(randomTime: CGFloat) {
let moveLeft = SKAction.moveByX(-kDefaultXToMovePerSecond, y: 0, duration: randomTime)
runAction(SKAction.repeatActionForever(moveLeft))
}
As you see I use the randomTime parameter for the duration:
startMoving(randomTime)
The same in the start()-function:
func start(randomTime:CGFloat)