Trying to reloadData() in viewWillAppear - ios

Question

I have a tabBarController and in one of the tabs I can select whatever document to be in my Favourites tab.
So when I go to the Favourites tab, the favourite documents should appear.
I call the reloading after fetching from CoreData the favourite documents:
override func viewWillAppear(_ animated: Bool) {
languageSelected = UserDefaults().string(forKey: "language")!
self.title = "favourites".localized(lang: languageSelected)
// Sets the search Bar in the navigationBar.
let search = UISearchController(searchResultsController: nil)
search.searchResultsUpdater = self
search.obscuresBackgroundDuringPresentation = false
search.searchBar.placeholder = "searchDocuments".localized(lang: languageSelected)
navigationItem.searchController = search
navigationItem.hidesSearchBarWhenScrolling = false
// Request the documents and reload the tableView.
fetchDocuments()
self.tableView.reloadData()
}
The fetchDocuments() function is as follows:
func fetchDocuments() {
print("fetchDocuments")
// We make the request to the context to get the documents we want.
do {
documentArray = try context.fetchMOs(requestedEntity, sortBy: requestedSortBy, predicate: requestedPredicate)
***print(documentArray) // To test it works ok.***
// Arrange the documentArray per year using the variable documentArrayPerSection.
let formatter = DateFormatter()
formatter.dateFormat = "yyyy"
for yearSection in IndexSections.sharedInstance.allSections[0].sections {
let documentsFilteredPerYear = documentArray.filter { document -> Bool in
return yearSection == formatter.string(from: document.date!)
}
documentArrayPerSection.append(documentsFilteredPerYear)
}
} catch {
print("Error fetching data from context \(error)")
}
}
From the statement print(documentArray) I see that the function updates the content. However there is no reload of documents in the tableView.
If I close the app and open it again, then it updates.
Don't know what am I doing wrong!!!

Answer 1

The problem is that you're always appending to documentArrayPerSection but never clearing it so I imagine the array was always getting bigger but only the start of the array which the data source of the tableView was requesting was being used. Been there myself a few times.

Answer 2

I assume that reloadData() is called before all data processing is done. To fix this you will have to call completion handler when fetching is done and only then update tableView.
func fetchDocuments(_ completion: #escaping () -> Void) {
do {
// Execute all the usual fetching logic
...
completion()
}
catch { ... }
}
And call it like that:
fetchDocuments() {
self.tableView.reloadData()
}
Good luck :)