The iOS Human Interface Guidelines say:
Use the system-provided Share button. Users are familiar with the meaning and behavior of thi
Here is the code. I am assuming you are inside ViewController so self has navigationItem property.
UIBarButtonItem *shareButton = [[UIBarButtonItem alloc]
initWithBarButtonSystemItem:UIBarButtonSystemItemAction
target:self
action:@selector(shareAction:)];
self.navigationItem.rightBarButtonItem = shareButton;