My title probably makes no sense, but I'll do my absolute best to explain it. So, basically, I have a UITableView that's getting data from Firebase. It has a listener, and any time values are changed on that tree, it updates the tableview. The thing is, I put this in viewDidLoad. (which seemed to make the most sense). Say, if the user goes over to the settings screen (a separate VC), and goes back, it reloads the tableview all over again. A couple users are complaining that it takes long to load the tableview when they come back to the main VC, and I was curious if I could keep the data there on THAT vc, so it's permanent until my listener detects a change in the database. Not sure if that makes any sense - but basically the only time I want the tableview to load data is the initial load, AND when data is changed on my backend. Not every time viewDidLoad gets called.
How do I make it so tableview loads data once, and the data stays even when switching view controllers
viewDidLoad is only called once during the lifecycle of a viewController. You are using a segue to return to your tableViewController from your settings viewController. A segue always instantiates a new destinationViewController. The only exception is the special unwind segue which returns to a previously instantiated viewController.
So, use an unwind segue to return to your tableViewController and your data will still be there and
viewDidLoad will not be called.