title: Autolayout constraints boundary condition
body: <p>I want view1 right constraint to be equal to view2 left constraint, but not if view2 moves past left of view1 (boundary condition). Here are the constraints I have:</p>
  
  <pre><code>    view1.leftAnchor.constraint(equalTo: contentView.leftAnchor, constant: 0).isActive = true
      view1.bottomAnchor.constraint(equalTo: contentView.bottomAnchor).isActive = true
      view1.topAnchor.constraint(equalTo: contentView.topAnchor).isActive = true
      view1.leftAnchor.constraint(greaterThanOrEqualToSystemSpacingAfter: contentView.leftAnchor, multiplier: 1.0).isActive = true
  
  
     let rightBoundaryConstraint = view1.rightAnchor.constraint(equalTo: iew2.leftAnchor)
  
      rightBoundaryConstraint.priority = UILayoutPriority(999)
      rightBoundaryConstraint.isActive = true
  </code></pre>
  
  <p>My doubt is this still does not determine position of view1 with 100% certainty. Am I missing something?</p>