MGTwitterEngine Not Working on iPad

Hello how to use MGTwitterEngine on iPad...

i have add this code on viewDidLoad but presentMod开发者_JS百科elViewController is not call i have debug the code... please let me know what i do wrong:

- (void)viewDidLoad {
    [super viewDidLoad];

    if(_engine) return;

    _engine = [[SA_OAuthTwitterEngine alloc] initOAuthWithDelegate:self];
    _engine.consumerKey = consumerKeyString;
    _engine.consumerSecret = consumerSecretKeyString;

    UIViewController *controller = [SA_OAuthTwitterController controllerToEnterCredentialsWithTwitterEngine: _engine delegate: self];

    if (controller) 
        [self presentModalViewController: controller animated: YES];
    else {
        tweets = [[NSMutableArray alloc] init];
        [self updateStream:nil];
    }

}

the presentModelView is call but twitter login view is not intiated .. please tell me thanks

I am using iOS 3.2