Question

I have to download an image from the server but I do not wish to create NSURLConnection, I know that UIKit is not thread safe so I tried this, just need a confirmation whether if this is safe or can it result in a crash (as of now it is working fine.)I tried the following

Look at the case 2 of the switch.

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
  switch (indexPath.row) {
    case 0:
    {
      CreateNewSurveyViewController *vc=[[CreateNewSurveyViewController alloc] init];
      [self.navigationController pushViewController:vc animated:YES];
      [vc release];
      break;
    }
    case 1:{
      MySurveyViewController *mySurveyViewController=[[MySurveyViewController alloc] init];
      [self.navigationController pushViewController:mySurveyViewController animated:YES];
      [mySurveyViewController release];
      break;
    }
    case 2:{

        self.progressHud.hidden = NO;
        [self performSelectorInBackground:@selector(loadProfileImage) withObject:nil];
      break;
    }
    default:
      break;
  }
}   
-(void)loadProfileImage {

    NSData* profileImageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:self.userAccount.profileImageURL]];
    [self performSelectorOnMainThread:@selector(launchSettingsView:) withObject:profileImageData waitUntilDone:YES];

}

-(void)launchSettingsView:(NSData*)profileImageData {
    self.userAccount.userImage = [UIImage imageWithData:profileImageData];
    self.progressHud.hidden = YES;
    SettingsViewController* settingsViewController=[[SettingsViewController alloc] init];
    settingsViewController.userAccount = self.userAccount;
    settingsViewController.delegate = self;
    [self.navigationController pushViewController:settingsViewController animated:YES];
    [settingsViewController release];
}

Answer 1

This looks safe to me. You do all your networking on a background thread, and then only touch the UI in the main thread method you call back to. Usually people will use GCD or NSOperationQueue but this should work too.