UIAlertController with text field check

UIAlertController

UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Title"
                                                                     message:nil
                                                              preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction *cancelAlertAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleDefault
                                                                handler:^(UIAlertAction * action) {}];
_saveAlertAction = [UIAlertAction actionWithTitle:@"Save" style:UIAlertActionStyleDefault
                                        handler:^(UIAlertAction * action) {
                                            
                                        }];
_saveAlertAction.enabled = NO;

[alert addTextFieldWithConfigurationHandler:^(UITextField *textField) {
    textField.placeholder = @"Enter a title...";
    [textField addTarget:self action:@selector(textChanged:) forControlEvents:UIControlEventEditingChanged];
}];
[alert addAction:cancelAlertAction];
[alert addAction:_saveAlertAction];
[self presentViewController:alert animated:YES completion:nil];

// ----------------------

- (void)textChanged:(id)sender
{
  UITextField *field = sender;
  _saveAlertAction.enabled = field.text.length > 0;
}