Why pushviewcontroller is not working after dismissing presentmodalviewcontroller?

I have one application that has list of videos.When user clicks any of videos the video is played using mpmovieplayercontroller in full screen mode and landscape mode.moviewplayer controller contains donatenow button in it.When user clicks that button then donation form should be opened.For that i am writing the following code

-(void)donate:(id)sender { [self dismissModalViewControllerAnimated:YES];

//[self presentModalViewController:moviePlayer animated:YES];

NSLog(@"Donation form method called");

DonationForm *dfvc=[[DonationForm alloc]initWithNibName:@"DonationForm" bundle:nil];
//[self presentModalViewController:dfvc animated:YES];
[self.navigationController pushViewController:dfvc animated:YES];
[dfvc release];

} with this mpmoviecontroller is removed.But it is not pushing the view to the donation form. how can i do that?

UPDATE:The issue got开发者_如何学Go solved by declaring the UIViewController *viewController in appDelegate and using it in above method as [appDelegate.viewControoller.navigationController pushViewController:dfvc animated:YES];