Swift Timer error when function has arguments

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