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Attempting to load the view of a view controller while it is deallocating is not allowed for UISearchViewController

This question has been asked before, but I am not able to get a clear explanation about this issue. I have a simple application with a tableview and a search function. In viewDidLoad(), I call setUpSearchView() which is defined like this

  let searchController = UISearchController(searchResultsController: nil)
  searchController.searchResultsUpdater = self
  searchController.hidesNavigationBarDuringPresentation = true
  searchController.dimsBackgroundDuringPresentation = false
  self.tableView.tableHeaderView = searchController.searchBar

This code doesn't not work properly. On the console, I can see this error 

Attempting to load the view of a view controller while it is deallocating is not allowed and may result in undefined behavior

Moreover, the searchcontroller does not animate properly and does not call updateSearchResultsForSearchController delegate when I type on the searchbar.

But, all these issues are easily fixed by making a minor change to the searchController initialization function. Rather than declaring the searchController as a local variable in the function, If I declare it an instance variable outside the method like this var searchController:UISearchController!, everything works, although I have no idea why.

Now the code will look like this 

var searchController:UISearchController!

In setUpSearchView()

 searchController = UISearchController(searchResultsController: nil)
 searchController.searchResultsUpdater = self
 searchController.hidesNavigationBarDuringPresentation = true
 searchController.dimsBackgroundDuringPresentation = false
 self.tableView.tableHeaderView = searchController.searchBar

Here is a link to the viewController on github: https://github.com/tmsbn/marvel_heroes/blob/master/avengers/HeroesListController.swift

Can someone explain why this happens? Is this a bug with swift? Or it is something in iOS that I don't know about.

Solution

  • If you are creating a variable in a function (viewDidLoad) it's lifetime is the same as that functions lifetime. In this case you are trying to set the table header view as a searchController that is being deallocated (it's lifetime is the same as viewDidLoads)

    When you create the variable outside of viewDidLoad and instantiate it later, the variable has the same lifespan as the viewController/class