create a global NSMutableArray

create a global NSMutableArray

I have a lot of View Controller and all use the same Class (ViewController).
In ViewController.m I have this code:
- (void)viewDidLoad
{
[super viewDidLoad];
pedidoNomeArray = [[NSMutableArray alloc] init];
pedidoValorArray = [[NSMutableArray alloc] init];
}
and when I go to View Controller number 2 my array pedidoNomeArray and
pedidoValorArray are null.
What I have to do to use the same array in all my View Controllers?
thanks