how to stop func update(_ currentTime: TimeInterval) in Spritekit - ios

Question

override func update(currentTime: NSTimeInterval) {
// ...
}
how to stop currentTime in update method?
I want to calculate time since game starts.
when player clicks pause button, current scene is paused successfully.
but, currentTime in update is moving.

Answer 1

When the scene is paused, update will not be called, try this code:
class GameScene: SKScene {
override func didMove(to view: SKView) {
let wait = SKAction.wait(forDuration: 2)
let pause = SKAction.run { self.isPaused = true }
self.run(SKAction.sequence([wait, pause]))
}
override func update(_ currentTime: TimeInterval) {
print("update")
}
}
"update" will be printed for the first 2 seconds only. This proves that pausing the scene will stop update. You are probably not pausing the scene, but a node in the scene on which all actions are run.
In addition to that, implementing a pause screen by pausing the scene isn't such a good idea because the user can't leave the pause screen by tapping if the scene is paused. Also, you can't show cool animations in the pause screen.
What I usually do is to have a background node. Every game sprite are added as a child of the background node. In the pause screen, the background pauses but the scene is still running. I then add the pause screen spirte as a direct child of the scene so that you can still interact with the pause screen.
You don't really need to "stop" the update method. You just need to check whether the game is paused in the method. If it is, return immediately.
If you want to measure how much time has passed since the player started the game, you can also use Date objects. Create a Date at the start of the game and another Date when the user pauses. Call the timeIntervalSince method and there you go!

Answer 2

I've implemented pause like the following, I think the code is self-explenatory but I've added some comments:
// BaseScene inherits from SKScene but adds some methods, e.g. for dealing with
// controller input.
class GameScene : BaseScene {
// The previous update time is used to calculate the delta time.
// The delta time is used to update the Game state.
private var lastUpdateTime: NSTimeInterval = 0
override func update(currentTime: CFTimeInterval) {
// NOTE: After pausing the game, the last update time is reset to
// the current time. The next time the update loop is entered,
// a correct delta time can then be calculated using the current
// time and the last update time.
if lastUpdateTime <= 0 {
lastUpdateTime = currentTime
} else {
let deltaTime = currentTime - lastUpdateTime
lastUpdateTime = currentTime
Game.sharedInstance.update(deltaTime)
}
}
// A method on BaseScene that is called when the player presses pause
// on controller.
override func handlePausePress(forPlayer player: PlayerIndex) {
paused = true
lastUpdateTime = 0
}
}
My Game singleton only makes use of the delta time (time difference since last call) when updating the game state.