Allocating and releasing of UI controllers - iphone

Question

I am new to iOS programming and I have read some useful articles on the release and allocation of memory and thought that i understand the concept. But during the actual coding, I can't seem to really apply the theory. I am really confuse over the fundamentals of iOS programming and hope that someone can help out. Thanks in advance!
1st behaviour - Some of the apps i see can maintain the current windows state when the iPhone home button is pressed so that when the app is launch next time, it will display the last state it is in.
2nd behaviour - Some other apps will behave like its a new startup everytime it is launch. Previously displayed text, images...etc will be cleared and it will always start at the first page.
What I wanted to do is like the 2nd behaviour - clear everything when the home button is pressed and start afresh everytime it is launch.
I have created a tab bar project. The codes below will result in the 1st behaviour.
I have tried releasing all the tab controllers at applicationDidEnterBackground instead at dealloc but it didn't work. It will still display the last screen.
My questions...
1) If i call release, shouldn't it destroy the window as well? eg. [NavController1 release]. It seems that the window can still work as usual...
2) What should I change to result in the 2nd behaviour?
3) If i assign tabBarController.viewControllers = nil, does it mean that the memory for the pages attached to it previously will be release?
4) Do i need to release IBOutlets variables? eg. UIWindow *window, UITabBarController, UITextField...etc. It didn't seem to give me memory leak even if i don't release them. The reason of this might be because I don't know how to kill the app. I tried to do the double click on the iphone home button to end the app but i still not able to get the debug to reach the dealloc function. An article says that if you alloc or retain it, you should release it. Since i'm not allocating anything here, can i not release it? Or is it possible to set autorelease?
#interface MyAppDelegate : NSObject <UIApplicationDelegate, UITabBarControllerDelegate> {
UIWindow *window;
UITabBarController *tabBarController;
UINavigationController *NavController1;
UINavigationController *NavController2;
}
#property (nonatomic, retain) IBOutlet UIWindow *window;
#property (nonatomic, retain) IBOutlet UITabBarController *tabBarController;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
NavController1 = [[UINavigationController alloc] init];
NavController2 = [[UINavigationController alloc] init];
//This view controller inherits UIViewController and has a xib
FirstViewController *firstpage = [[FirstViewController alloc] init];
firstpage.title = #"First Page";
//These view controllers inherits UIViewController and delegate of UINavigationControllerDelegate and has a xib
SecondViewController *secondpage = [[SecondViewController alloc] init];
secondpage.title = #"Second Page";
[NavController1 pushViewController:secondpage animated:YES];
[secondpage release];
ThirdViewController *thirdpage = [[ThirdViewController alloc] init];
thirdpage.title = #"Third Page";
[NavController2 pushViewController:thirdpage animated:YES];
[thirdpage release];
// Add them as children of the tab bar controller
tabBarController.viewControllers = [NSArray arrayWithObjects:firstpage, NavController1, NavController2, nil];
// Don't forget memory management
[firstpage release];
// Add the tab bar controller's view to the window and display.
[window addSubview:tabBarController.view];
[window makeKeyAndVisible];
return YES;
}
- (void)applicationDidEnterBackground:(UIApplication *)application {
/*
Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
If your application supports background execution, called instead of applicationWillTerminate: when the user quits.
*/
}
- (void)applicationWillEnterForeground:(UIApplication *)application {
/*
Called as part of transition from the background to the inactive state: here you can undo many of the changes made on entering the background.
*/
}
- (void)dealloc {
[NavController1 release];
[NavController2 release];
[tabBarController release];
[window release];
[super dealloc];
}

Answer 1

1) As long as the retain count is 1 your view controller will be released by calling release.
In your code, dealloc will never be called, and therefore your view controllers will not be released anyway. You need to release everything in applicationDidEnterBackground...
2) in applicationDidEnterBackground do something like:
[NavController1 release];
NavController1 = nil;
[NavController2 release];
NavController2 = nil;
tabBarController.viewControllers = nil;
then recreate everything again in
(void)applicationWillEnterForeground:(UIApplication *)application
3) doing this will release firstpage, NavController1 and NavController2 (and any other view controllers you may have added)
4) yes you should. You do not get a memory leak in this instance because the delegate never gets dealloc'd and therefore there is still a valid reference to the objects. No you cannot autorelease as autorelease will release the object when the call stack returns to the run loop.