Question

I have a method used to save an image when the user clicks Save.
I use performSelectorInBackground to save the image, the viewcontroller is popped and the previous viewcontroller is shown.

I want the table (on the previousUIViewController) to reload its data when the imagesaving is done.

How can I do this?

The save method is called like this:

[self performSelectorInBackground:@selector(saveImage) withObject:nil];
[self.navigationController popViewControllerAnimated:YES];

Answer 1

In your saveImage method, post a notification just after finishing saving the image and before returning from the method. Something like this:

// post notification
    [[NSNotificationCenter defaultCenter] postNotificationName:@"ImageSaved" object:nil];

In the controller handling the table, implement

- (void) imageSaved:(NSNotification *)notification{

    [self.tableView reloadData];

}

and in its viewDidLoad method add the following code to register for notifications:

[[NSNotificationCenter defaultCenter] addObserver:self
                                selector:@selector(imageSaved:)
                                                 name:@"ImageSaved" object:nil];

finally, unregister in the dealloc method adding

[[NSNotificationCenter defaultCenter] removeObserver:self];