title: How to disable a constraint programmatically?
body: <p>How to disable a constraint programmatically?</p>
  
  <p>I have two constraints, that the priority of one depends for the other. As far as I know the constraints priority can’t change programmatically when they are installed (it throw me an error), So the idea is, when X occurs the constraint A is disable and the constraint B is enable, and when Y occur A is enable and B disable</p>
  
  <pre><code>IBOutlet weak var constraint_A
  IBOutlet weak var constraint_B
  
  ... 
  
  func configureViews() {
     if x {
          constraint_A.disable = true
          constraint_B.disable = false
     }  else {
          constraint_A.disable = false
          constraint_B.disable = true
     }
  }
  ...
  </code></pre>