title: Not able to set constraints in XIB - Xcode 11.3.1
body: <p>I created a project in Swift. I added view controller file and one XIB using right click on the project - > Add Files to projectname -> Empty (xib) file.</p>
  
  <p>After adding the xib file, i removed the view and added View Controller. Under the View controller , i have added few button. But i am not able set the constraints.But if i add the View object instead of View Controller, i am able to set the constraints. I don't understand why the xib constraints are disabled for View controller. Attached the screen shot</p>
  
  <p><a href="https://i.stack.imgur.com/IwIdr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/IwIdr.png" alt="enter image description here"></a></p>