Swift Timer error when function has arguments - swift

Question

I'm trying to make a function that activates every one second, which adds 1 to a variable (texttimer) and adds a letter to a string (typedStory), which is displayed on a label (storyLabel).
Everything worked fine until I added an argument (finalStory) to the function. Now I'm getting an an error:
-[__NSCFTimer substringToIndex:]: unrecognized selector sent to instance
Here's the code I have:
func textTypeWelcome(finalStory: NSString){
var newTimer2 = Timer.scheduledTimer(timeInterval: 0.05, target: self, selector: #selector(GameScene.textTypeWelcome), userInfo: finalStory, repeats: false)
texttimer += 1
typedStory = finalStory.substring(to: texttimer)
storyLabel.text = typedStory
}
The code works, however doesn't do what I want if I remove the argument and put userInfo to nil.
Anyone know of a solution? Thanks!

Answer 1

No, that cannot work, the action method takes the timer as parameter – what the error message tells you – and you get finalStory from the userInfo parameter.
func textTypeWelcome(timer: Timer) {
let finalStory = timer.userInfo as! String
var newTimer2 = Timer.scheduledTimer(timeInterval: 0.05, target: self, selector: #selector(GameScene.textTypeWelcome), userInfo: finalStory, repeats: false)
texttimer += 1
typedStory = finalStory.substring(to: texttimer)
storyLabel.text = typedStory
}
Try this out in a Playground
class Foo : NSObject {
let string = "Hello World"
var counter = 1
var typedStory = ""
var timer = Timer()
override init() {
super.init()
timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(timerFired), userInfo: nil, repeats: true)
print("timer started")
}
func timerFired(timer : Timer) {
typedStory = string.substring(to: string.index(string.startIndex, offsetBy: counter))
print(typedStory)
if typedStory == string {
timer.invalidate()
print("timer stopped")
} else {
counter += 1
}
}
}
let foo = Foo()
You have to add the lines
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true
to allow asynchronous API