Convenience Initialization of Uinavigationcontroller Subclass Makes Subclass Constant Init Twice

Purpose of init pattern in obj-c and its use

1. The initializer pattern is necessary, because the super class whose initializer you are calling, can return any kind of object, not necessarily the instance of that class. That's how, for example, NSString works, it's actually a cluster of classes implementing different kinds of strings optimized for different usage patterns. So calling self = [super init] for NSString descendant makes self, for example, an NSCFString instance.

2. There's a pattern called Designated Initializer in Objective C. If the class has many initializer, one of them is chosen as designated, and all the other should be implemented by calling it, not the super. This is important for correctly overriding initializers in child classes, you should initialize only the designated one, and it will be called under all circumstances (assuming your code is well-written and takes advantage of designated initializers, of course :)

viewDidLoad is called before whole init method is executed

You are not guaranteed to have viewDidLoad to be called only after the init method is done. viewDidLoad gets called when a view-controller needs to load its view hierarchy.

Internally, TabBarController's init method (by calling super.init) is doing something which is causing the view to load.

This applies to all view-controllers. For example: if you create a UIViewController subclass and do anything with its view property on init, like adding a subview, or even just setting the backgroundColor property of the view - you will notice the same behavior.

How to create backBarButtomItem with custom view for a UINavigationController

I'm fairly certain that the backBarButtonItem is a read-only property. Instead of modifying the backBarButtonItem, try setting a custom leftBarButtonItem and hide the backBarButtonItem:

self.navigationItem.leftBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Prout" style:UIBarButtonItemStyleDone target:nil action:nil] autorelease];
self.navigationItem.hidesBackButton = YES;

You will also need to make sure you hook up the custom button to call the back action on the UINavigationBar.

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