How to add UIBarButtonItem to QLPreviewController - objective-c

Question

I already read this question QLPreviewController remove or add UIBarButtonItems but it's not what I'm looking for. I would like to keep the "Print" button in the navigation Bar but also add a new "Delete Document" button in the navigation bar.
I tried this:
QLPreviewController *previewer = [[[QLPreviewController alloc] init] autorelease];
[previewer setDataSource:self];
UIBarButtonItem *saveButton = [[UIBarButtonItem alloc]initWithTitle:#"Salva Documento" style:UIBarButtonItemStyleBordered target:self action:#selector(saveFileToDocuments)];
NSArray *buttons = [NSArray arrayWithObjects:[[previewer navigationItem]rightBarButtonItem],saveButton, nil];
[[previewer navigationItem]setRightBarButtonItems:buttons];
But it didn't work.

Answer 1

Because you said "4.x will be fine", there's your problem.
The documentation for UINavigationItem [setRightBarButtonItems: animated:] (documentatin linked there for you) say that this function only works on iOS 5.0 and newer.
It will not work on iOS 4.0.
Also, you should add an animated: parameter to that setRightBarButtonItems: call.

Answer 2

UIBarButtonItem *rbb;
-(void)addRightButton{
if (!rbb) {
UIButton *orderButton = [UIButton buttonWithType:UIButtonTypeCustom];
orderButton.frame = CGRectZero;
rbb = [[UIBarButtonItem alloc] initWithCustomView:orderButton];
}
self.navigationItem.rightBarButtonItem = rbb;
}
- (void)viewDidLoad{
[super viewDidLoad];
[self performSelector:#selector(addRightButton) withObject:nil afterDelay:0.2];
}
-(void)viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
[self addRightButton];
}