how to push views iphone?

i'm new to iphone development and i need some guidance in pushing views. I have the following application scenario "press on button ->switch view (contains a table)->press on table cell ->switch view".

To switch when i press the button i use the following code :

MapView *screen = [[MapView alloc] initWi开发者_运维知识库thNibName:nil bundle:nil];
screen.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:screen animated:YES];
[screen release];

Then to push another view i want to use this code (but it does not work - and im asking why?)

Newclass *nextController = [[Newclass alloc] initWithItem:theItem];
    [self.navigationController pushViewController:nextController animated:YES];
    [nextController release];

You want to push this view from your MapView? Looks like you don't have a UINavigationController which is needed to push view controllers like that.

Update the first part of your code to put the MapView inside UINavigationController, than you can push other views onto it with that second part of code you have.

MapView *screen = [[MapView alloc] initWithNibName:nil bundle:nil];
UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:screen]; // this puts the MapView onto navigation controller
navController.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal; // you will present the navController instead of screen so change it's modalTransitionStyle
[self presentModalViewController:navController animated:YES]; // present it
[screen release];
[navController release]; // don't forget to release