How do I show/hide a UIBarButtonItem?

Question

I created a toolbar in IB with several buttons. I would like to be able to hide/show one of the buttons depending on the state of the data in the main window.

Answer 1

If you are using Swift 3

if (ShowCondition){
   self.navigationItem.rightBarButtonItem = self.addAsset_btn 
 } 
else {
   self.navigationItem.rightBarButtonItem = nil
 }