UITableView not updating when switching between tabs - ios

Question

Preface: I've tried adding tableView.reloadData() to viewWillAppear (...and viewDidLoad, viewDidAppear, etc.) of the UITableViewController that's not updating. I threw in setNeedsDisplay for S's & G's, too.
I have a UITabBarController with 3 tabs on it. Each tab is a TableViewController is backed by Core Data and is populated with NSManagedObjects from one NSManagedObjectContext.
In TableViewController1 I make changes to the cells, the tableView reloads properly and reflects the changes. If I click the tab for TableViewController2, the changes made on TVC1 aren't reflected.
The changes made on TVC1 are persisting between launches, as I see them on TVC2 when I close the app and relaunch it.
What am I missing? Any ideas would be greatly appreciated.
Update
Here's the code in question:
func markFavorite(sender: AnyObject) {
// Store the sender in case you need it later. Might not need this.
clickedFavoriteButton = sender as! UIButton
if resultsSearchController.active {
let indexPath = sender.tag
let selectedSound = self.filteredSounds[indexPath]
print("markFavorite's sender tag is \(indexPath)")
if selectedSound.favorite == 1 {
selectedSound.favorite = 0
} else {
selectedSound.favorite = 1
}
saveManagedObjectContext()
} else {
let indexPath = sender.tag
let selectedSound = self.unfilteredSounds[indexPath]
print("markFavorite's sender tag is \(indexPath)")
if selectedSound.favorite == 1 {
selectedSound.favorite = 0
} else {
selectedSound.favorite = 1
}
saveManagedObjectContext()
}
}
func saveManagedObjectContext() {
if managedObjectContext.hasChanges {
do {
try self.managedObjectContext.save()
} catch {
// catch error here
}
}
self.tableView.reloadData()
}

Answer 1

You should always use a NSFetchedResultsController to display Core Data items in a table view. It comes with delegate methods that update your table as the underlying data changes (even before saving).
To get started, examine the Xcode template (Master-Detail) implementation. Once you get the hang of it you will love it. Everything works pretty much out of the box.

Answer 2

You may have to trigger context.save() manually because core-data isn't saving the data right away.
let context = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext!
runOnMain() {
do {
try! self.context.save()
} catch let error as NSError {
//Handle any upcoming errors here.
}
}
Its important to run the method on the main thread otherwise you will get an error.
this method should do the job:
func runOnMain(block: dispatch_block_t) {
if NSThread.isMainThread() {
block()
}else{
dispatch_sync(dispatch_get_main_queue(), block)
}
}
Please let me know if this approach worked for you.

Answer 3

You should not try to reload data at any point in view controller lifecycle. Instead create delegates for each tab bar controller, set them properly and call delegate methods only when something really change in your data source. If you are not familiar with delegation you can learn more about it here