Start computations automatically only after view has appeared

Question

I have a view controller that just shows progress during calculations. I put the method calls

in viewDidLoad but the problem is the view only appears once the calculations are done! How

could I automatically launch the calculations after the view has appeared on screen?

Answer 1

You may use GCD. Here is Raywenderlich tutorial

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

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
        //Calculations
        dispatch_async(dispatch_get_main_queue(), ^{
            //Update UI must be here
        });
    });
}