Code in viewDidLoad runs every time it is called

Question

Hi all I am doing a course in Udemy, and the code calls for placing code in the viewDidLoad function as shown below:

    override func viewDidLoad() {
    super.viewDidLoad()

    placesArray.append(["name":"Taj Mahal", "lat":"27.175607", "lon":"78.042112"])

}

The array append should only run once, however, when I segue to another viewController and come back, it runs the code to append again. So I now have an array with 2 rows, both of which are Taj Mahal.

I thought that the viewDidLoad function only runs code once?

Is there a way around this?

Thanks.

Addendum: I am using Swift, so I don't see any alloc and init while creating and launching the viewController. And weird as it sounds, the video tutorial has it working in the viewDidLoad and the trainer is using the storyboard to segue from the initial table view controller to a map view on a view controller and just has a back button on the map view that segue's back to the table view controller via the storyboard as well. - Could be because I have the latest version of the Swift language and the trainer was using an earlier version, (cause I noticed some slight differences in coding earlier) but you never know. Either way whenever he touches the back button it does not run the append code anymore. I am trying to get in contact with the trainer as some of the suggestions here, though they are good don't seem to work. I will put the solution in here once I get in contact with the trainer.

Maybe when u segue to the other viewController the old one is dealloc, and when u came back it's loads again?! — gran33
You're probably coming back with a segue that's not an unwind. You should not do that. It creates a new instance, it doesn't actually come back. — rdelmar

Ian MacDonald Ian MacDonald · Accepted Answer · 2014-11-05T15:04:06

The viewDidLoad method is called when your view controller's view finishes loading. The view will load when a view controller's view property is nil and something attempts to access it.

UIViewController *myVC = [[UIViewController alloc] init];
UIView *aView = myVC.view; // this loads myVC's view; viewDidLoad is called when it completes loading.

If the view has unloaded (usually due to memory limitations), it will be called when the view property is next accessed.

Manipulation of data sets should generally not be done within view methods. Consider moving this to the init of the view controller (or to a different "datasource" class).

Code in viewDidLoad runs every time it is called

3 Answers