How to tell a viewcontroller to update its UI from another class

Question

I am trying to understand how updating of a viewController that is currently visible works. I have ViewControllerA and ClassA. I want to tell ViewControllerA to reloadData on the tableview from ClassA. What is the best way to go about doing this?

I have found this question and answer but I dont think this will work in my situation or I am not understanding it correctly.

Answer 1

The easiest way without knowing your setup would be to use NSNotificationCenter. Here is what you could do:

In ViewControllerA add in hooks for NSNotificationCenter:

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    //Register for notification setting the observer to your table and the UITableViewMethod reloadData. So when this NSNotification is received, it tells your UITableView to reloadData
    [[NSNotificationCenter defaultCenter] addObserver:self.table selector:@selector(reloadData) name:@"ViewControllerAReloadData" object:nil];
}

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];

    //Need to remove the listener so it doesn't get notifications when the view isn't visible or unloaded.
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

Then in ClassA when you want to tell ViewControllerA to reload data just post the NSNotification.

- (void)someMethod {
    [[NSNotificationCenter defaultCenter] postNotificationName:@"ViewControllerAReloadData" object:nil];
}