Swift RunLoop blocks table view

Question

So, I have a timer which increments a variable by one in my app delegate every 0.1 seconds. In my tableViewController, I have this number displayed in a cell. In the controller there is ANOTHER timer which reloads visible cells. Everything worked, apart for the fact that once scrolling through the tableView, the number stopped changing until the table view wasn't released. I have read that the fix for this was:

RunLoop.current.add(tableTimer, forMode: RunLoopMode.commonModes)

Where tableTimer is my cell reload timer. Nevertheless, this works, but once scrolling through the view it is extremely laggy and is 0% fluid, as it normally is. Any fix? Thanks.

EDIT:

Creating the timer:

func scheduledTimerWithTimeInterval(){
    reloadTimer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(self.reloadTV), userInfo: nil, repeats: true)
    RunLoop.current.add(earningTimer, forMode: RunLoopMode.commonModes)
}

Updating table view:

@objc func reloadTV() {
    self.tableView.beginUpdates()
    self.tableView.reloadRows(at: self.tableView.indexPathsForVisibleRows!, with: .none)
    self.tableView.endUpdates()
}

This is likely related to cell dequeuing. Can you post the code updating the cell? — Cristik, Mar 09 '18 at 20:21
You seem to be reloading the table view 10 times per second. No wonder you have performance problems :) — Cristik, Mar 09 '18 at 20:24
Put the timer in the cell. Invalidate it when the cell gets out of screen. — Cristik, Mar 09 '18 at 20:26
And increase the time interval to 1 second, if you need to update the UI once per second — Cristik, Mar 09 '18 at 20:26
@cristik do you have any place I can go to, to see how it is done? How can I reload a cell? — Riccardo Perego, Mar 09 '18 at 20:26
Check [here](https://developer.apple.com/documentation/uikit/uitableview), especially the "Reloading the Table View" section. — Cristik, Mar 09 '18 at 20:29
You should reload the row that the timer operates on, not necessarily the visible ones. Also make sure the timer correctly works — Cristik, Mar 09 '18 at 21:25

score 0 · Accepted Answer · answered Mar 09 '18 at 22:08

Reloading a table view every .1 seconds for a label in a cell is quite stupid. For many several reasons. The optimum way to solve this issue is to loop through all visible index paths, create a cellForRowAtIndexPath with the index paths and than modify the cell title directly from there, in the following way:

@objc func reloadTV() {

    for myIP in (tableView.indexPathsForVisibleRows) {
        let cell = tableView.cellForRow(at: myIP)
        cell.textLabel?.text = changingVariable
    }

}

Swift RunLoop blocks table view

1 Answers1