Invalidate and create new instance of timer

Question

I have a timer that i am running from within a closure to help perform some ui update (progress bar). It works for the first item, but i want it to work for multiple items. So each time the closure is run a new instance of the timer is run and the new userInfo.

    // dispatch and add run loop to get it to fire
    DispatchQueue.main.async(execute: {
        timer = Timer.init(timeInterval: 0.25, target: self, selector: #selector(self.downloadTimer(_:)), userInfo: [innerCell, collectionView, indexPath], repeats: true)
        RunLoop.main.add(timer, forMode: RunLoopMode.defaultRunLoopMode)
    })

When this function below is finished i want the timer to be recreated and pass new userInfo to the selector..

func downloadTimer(_ timer: Timer) {

    // need to pass arguments to timer as array inside userInfo
    // then create dictionary and extract

    let dict = timer.userInfo as! NSArray
    let cell = dict[0] as! InnerCollectionCell
    let collectionView = dict[1] as! UICollectionView
    let indexPath = dict[2] as! IndexPath


    // the index path isnt getting reset

    // without casting the progress bar in each cell was displaying when coming back to DownloadCollectionController
    if let downloadingCell = collectionView.cellForItem(at: indexPath) as? InnerCollectionCell {

        DispatchQueue.main.async(execute: {

            downloadingCell.progressBar.isHidden = false
            downloadingCell.contentView.bringSubview(toFront: cell.progressBar)
            downloadingCell.progressBar.setProgress(downloadProgress, animated: true)
            downloadingCell.setNeedsDisplay()


            if downloadProgress >= 1.0 {
                print("TIMER STOPPED")
                downloadingCell.progressBar.isHidden = true
                //downloadQueue.operations[0].cancel()
                timer.invalidate()
                collectionView.reloadItems(at: [indexPath])

            }
        })
    }

}

The closure containing the timer = Timer is re-run but the new user info is not passed to the timer, it just keeps running with the original userInfo. If i invalidate the timer it can no longer be fired?

Ive tried creating it locally to the initial firing:

var timer = Timer()
timer = Timer.init(timeInterval: 0.25, target: self, selector: #selector(self.downloadTimer(_:)), userInfo: [innerCell, collectionView, indexPath], repeats: true)

But it doesn't recreate the timer and i want to be able to stop it if the user leaves the viewcontroller.

Is there a better way of achieving this? I know your not supposed to be able to retire a timer. there must be a way of creating a unique instance of it each time.

---- EDIT ----

This is what the index paths print as:

[0, 5]
[0, 5]
[0, 5]

[0, 5]
[0, 2]
[0, 5]
[0, 2]

[0, 1]
[0, 1]
[0, 1]
[0, 1]

So its taking a while to invalidate the timer and in that time the timer has been re-fired and the function is using the old index path until progress = 1

---- EDIT ----

The only place invalidation takes place is when progress >= 1

            if downloadProgress >= 1.0 {
                timer.invalidate()
                downloadingCell.progressBar.isHidden = true
                downloadingCell.progressBar.progress = 0
                collectionView.reloadData()
            }

Then because the timer is fired from cellForItemAt if the cell meets certain conditions, when collectionView.reloadData() is called the timer should be re-validated and the updated userInfo sent.

So this is the block inside cellForItemAt:

for operation in downloadQueue.operations {
        if operation.name == self.multiPartArray[collectionView.tag][indexPath.item].name  {
            // edits for all queued operations
            innerCell.spinner.isHidden = false
            innerCell.spinner.startAnimating()
            innerCell.contentView.bringSubview(toFront: innerCell.spinner)
            innerCell.spinner.activityIndicatorViewStyle = .gray
            innerCell.spinner.color = UIColor.darkGray

        // hide the progress on all in queue it will be pushed to front when needed
        innerCell.progressBar.isHidden = true

        if operation.name == downloadQueue.operations[0].name {
            // edits for the active downlaod in queue

            // hide the spinner for currently downloading cell
            // innerCell.spinner.isHidden = true
            innerCell.spinner.isHidden = false
            innerCell.spinner.startAnimating()
            innerCell.contentView.bringSubview(toFront: innerCell.spinner)
            innerCell.spinner.activityIndicatorViewStyle = .gray
            innerCell.spinner.color = UIColor.blue

                DispatchQueue.main.async(execute: {
                    let timer = Timer.init(timeInterval: 0.5, target: self, selector: #selector(self.downloadTimer(_:)), userInfo: [innerCell, collectionView, indexPath, collectionView.tag], repeats: true)
                    RunLoop.main.add(timer, forMode: RunLoopMode.defaultRunLoopMode)
                })

            break
        } else {
            // edits spinner that isnt currently downloading
            innerCell.progressBar.isHidden = true
            innerCell.spinner.color = UIColor.darkGray
        }
    } else {
        // edits the spinner that isnt in queue
        innerCell.progressBar.isHidden = true
        innerCell.spinner.color = UIColor.darkGray
    }
}

I realise its not the most elegant solution but I've got nested collection views that have probably not been set up entirely properly so ill settle for a work around in this case.

And the downloadTimer:

func downloadTimer(_ timer: Timer) {

    // need to pass arguments to timer as array inside userInfo
    // then create dictionary and extract
    let dict = timer.userInfo as! NSArray
    let cell = dict[0] as! InnerCollectionCell
    let collectionView = dict[1] as! UICollectionView
    let indexPath = dict[2] as! IndexPath
    let tag = dict[3] as! Int

    print(indexPath)

    // without casting the progress bar in each cell was displaying when coming back to DownloadCollectionController
    if let downloadingCell = collectionView.cellForItem(at: indexPath) as? InnerCollectionCell {

       // self.outerCollectionView.reloadItems(at: [IndexPath(item: tag, section: 0)])

        DispatchQueue.main.async(execute: {

            downloadingCell.spinner.isHidden = true
            downloadingCell.progressBar.isHidden = false
            downloadingCell.contentView.bringSubview(toFront: cell.progressBar)
            downloadingCell.progressBar.setProgress(downloadProgress, animated: true)
            downloadingCell.setNeedsDisplay()

            if downloadProgress >= 1.0 {
                timer.invalidate()
                downloadingCell.progressBar.isHidden = true
                downloadingCell.progressBar.progress = 0
                collectionView.reloadData()
            }
        })
    }
}

Answer 1

Best way to schedule and use a time is like this:

//schedules timer at an 4 seconds interval + pass desired userInfo 
var myTimer = Timer.scheduledTimer(timeInterval: 4.0
        , target: self, selector: #selector(timerSelector), userInfo: nil, repeats: true)

//timer selector peform your actions there and  
func timerSelector(dt:Timer){  
}

//invalidate timer when needed like this
myTimer?.invalidate()

Also to reschedule the timer just call again Timer.scheduledTimer