How can I lock an async function so it waits for the first call to finish before running again

Question

I dont want the same async function running multiple times in a row. I want the function to wait until the first call of the function to finish before having the ability to run again

I've tried unwiring the event and then wiring it back up but that doesn't seem to stop the function from being called multiple times

code:

 func scrollViewDidScroll(scrollView: UIScrollView)
{
 myScrollView.delegate = nil
 myAsync()
 myScrollView.delegate = self
}

I've also tried setting the delegates to nil and self inside of the function but that didn't work either

Answer 1

You could introduce a Bool property running and set it to true when the async function is called. When the async function finishes set it back to false . Then you only call the async function when running == false

func scrollViewDidScroll(scrollView: UIScrollView) {
    if !running {
        running = true
        myAsync()
    }
}

func myAsync() {
    // do your async stuff
    running = false // this has to be done on the main thread after the async stuff has finished
}