UINavigationItem lifecycle - iphone

Question

As far as I understand the SDK documentation UIViewController's navigationItem lifecycle is bound to the controller itself and not to the controller's view. I.e. in the default implementation it is created on-demand and destroyed with the view controller - with all contents like button items and titleView. Given that both button items and the titleView may be represented by UIView instances - does that mean that once created these views will stay in memory until controller is destroyed and live through all memory warnings?
What is the sense behind this design decision? Is impact for memory usage considered too small to bother? Is it really small for an application which is using customized nav bar buttons/titles everywhere?
It is easy to explicitly bound some of the navigationItem properties to the controller's view lifecycle - like setting titleView in -viewDidLoad and dropping it in -viewDidUnload (self.navigationItem.titleView = nil). But the navigationItem property documentation suggests to avoid this pattern. Are there any other potential problems other than the given example with back button?

Answer 1

Added a category (snippet2) to track the retain count and the destruction of the navigation items, feel free to do the same :) Seems like it is not deallocated with the memory warning. An explanation would come from a common sense that view controllers don't have to be used with the navigation controller: that should be why the nav-item is added with a separate category (snippet1) and it's lifecycle must be managed with a nav-controller, not the view controller instance itself.
In the case the custom nav-items are so heavy that you need to release it whenever possible,
i would leave the default implementation, add custom nav-items category and manage this items manually as i wish (again through overriding required UINavigationController methods like nav-controllers didReceiveMemoryWarning, pushViewController:animated:, popViewControllerAnimated:animated:). I can't imagine such a case when it is really needed however.
snippet 1
#interface UIViewController (UINavigationControllerItem)
#property(nonatomic,readonly,retain) UINavigationItem *navigationItem; // Created on-demand so that a view controller may customize its navigation appearance.
#property(nonatomic) BOOL hidesBottomBarWhenPushed; // If YES, then when this view controller is pushed into a controller hierarchy with a bottom bar (like a tab bar), the bottom bar will slide out. Default is NO.
#property(nonatomic,readonly,retain) UINavigationController *navigationController; // If this view controller has been pushed onto a navigation controller, return it.
#end
snippet 2
#implementation UINavigationItem (Logs)
- (id)init
{
NSLog(#"I'm initialized (%#)", [self description]);
self = [super init];
return self;
}
-(void) release
{
NSLog(#"I'm released [%d](%#)", [self retainCount], [self description]);
[super release];
}
-(void) dealloc
{
NSLog(#"I'm deallocated [%d](%#)", [self retainCount], [self description]);
[super dealloc];
}
#end