why setBackBarButtonItem not work in the childViewController viewDIdLoad? - iphone

Question

I want to custom the backBarButtonItem in the navigationItem,
here is my code
- (void)viewDidLoad
{
[super viewDidLoad];
UIBarButtonItem *back = [[UIBarButtonItem alloc] initWithTitle:#"Back"
style:UIBarButtonItemStylePlain
target:nil
action:nil];
[[self navigationItem] setBackBarButtonItem:back];
}
but it didn't work while I used the leftBarButtionItem can work.
I don't know ,can anybody give me an answer?

Answer 1

- (void)viewDidLoad
{
[self.navigationItem setHidesBackButton:YES];
UIBarButtonItem *cancelNavButton = [[UIBarButtonItem alloc] initWithTitle:#"Cancel" style:UIBarButtonItemStylePlain target:self action:#selector(dismissController)];
[self.navigationItem setLeftBarButtonItem:cancelNavButton];
}
- (void)dismissController
{
[self.navigationController popViewControllerAnimated:YES];
}

Answer 2

You shouldn't have to create the back button yourself if you are pushing your view controllers using the UINavigationController's pushViewController:animated: method. This will push the new ViewController on the NavigationControllers stack and give you an automatic back button with the title of the previous ViewController.
The reason your button doesn't work is the target: and action: parameters are nil you could bind them to the UINavigationController's popViewControllerAnimated: method to achieve the same action as the default back button.
- (void)viewDidLoad
{
[super viewDidLoad];
UIBarButtonItem *back = [[UIBarButtonItem alloc] initWithTitle:#"Back"
style:UIBarButtonItemStylePlain
target:[self navigationController]
action:#selector(popViewControllerAnimated:)
];
[[self navigationItem] setBackBarButtonItem:back];
}

Answer 3

- (void)viewDidLoad
{
[super viewDidLoad];
self.navigationItem.hidesBackButton = YES;
UIBarButtonItem *back = [[UIBarButtonItem alloc] initWithTitle:#"Back"
style:UIBarButtonItemStylePlain
target:nil
action:nil];
self.navigationItem.leftBarButtonItem = back;
}