Inserting alert view but not functioning

Question

I have a situation where i need to alert users that the next view controller accessed is "Data Loading".

I added this to the FirstViewController button action:

- (IBAction)showCurl:(id)sender {
    UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Please Wait" message:@"Acquiring data from server" delegate:self cancelButtonTitle:@"OK!" otherButtonTitles:nil];
    [alert show];
    SecondViewController *sampleView = [[SecondViewController alloc] init];
    [sampleView setModalTransitionStyle:UIModalTransitionStylePartialCurl];
    [self presentModalViewController:sampleView animated:YES];
}

it doesn't work. It loads to SecondViewController and only pops up after the SecondViewController is loaded.

So i tried on the SecondViewController itself. The SecondViewController extracts data from a remote server which is the reason its going to take a while to download depending on Internet connectivity. So i decided to add the UIAlertView in the function:

- (NSMutableArray*)qBlock{
    UIAlertView *alert_initial = [[UIAlertView alloc]initWithTitle:@"Loading" message:nil delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alert_initial show];

    NSURL *url = [NSURL URLWithString:@"http://www.somelink.php"];
    NSError *error;
    NSStringEncoding encoding;
    NSString *response = [[NSString alloc] initWithContentsOfURL:url 
                                                    usedEncoding:&encoding 
                                                           error:&error];
    if (response) {
        const char *convert = [response UTF8String];
        NSString *responseString = [NSString stringWithUTF8String:convert];
        NSMutableArray *sample = [responseString JSONValue];
        return sample;
    }
    else {
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"ALERT" message:@"Internet Connection cannot be established." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show];
    }
    return NULL;
}

This doesn't work too. And to top it off, i tried to off internet connection to see if the second alert pops up to alert user that there's no internet connection. The second alert doesn't work too.

Answer 1

For the first part of the question: the show method of UIAlertView does not blocks the current thread, so the execution continues and the behavior you have is expected. What you have to do is implement one of the UIAlertViewDelegate's methods and set the alert's delegate property to self. So when the alert is dismissed, you can show your SecondViewController.

For the second part if you're having your qBlock method executed in a background thread then it's normal you alert not to be shown again - you need to show your alert in the main thread, where the UI is running. To do that change your else statement with the following:

else
{
    dispatch_async(dispatch_get_main_queue(), ^{
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"ALERT" message:@"Internet Connection cannot be established." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show]; 
    });
}

Hope this helps.