iOS开发怎样在导航条上添加多个item

1. 如何设置title

2. 如何设置 leftBatButtonItem和 rightBarButtonItem
UIBarButtonItem *leftButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"左边按钮" style:UIBarButtonItemStylePlain
target:self action:@selector(OnLeftButton:)];
self.navigationItem.leftBarButtonItem = leftButtonItem;
[leftButtonItem release];

UIBarButtonItem *rightButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"右边按钮" style:UIBarButtonItemStylePlain
target:self action:@selector(OnRightButton:)];
self.navigationItem.rightBarButtonItem = rightButtonItem;
[rightButtonItem release];