title: UINavigation button change
body: <p>I have 3 view controllers, 2 of them with some data that i display in the third controller..
  I want to change the third controller navigation button according to from which controller i read the data..</p>
  
  <p>Example: If i pressed on row in controller 1, i want the button on controller 3 to be "edit"
  and if i pressed on a row in controller 2 i want the button on controller 3 to disappear..</p>
  
  <p>How can i do so?</p>
  
  <p>I am pretty new to iOS development so an example with some explanation would be great..
  thank you!</p>