title: NSLayoutConstraint outlets are allways nil while other outlets aren't
body: <p>I'm instantiating a shop via a xib:</p>
  
  <pre><code>let cShop = UINib(nibName: "connectedShop", bundle: nil).instantiateWithOwner(nil, options: nil)[0] as! connectedShop
  </code></pre>
  
  <p>This shop has assigned this custom class:</p>
  
  <pre><code>    import Foundation
  import UIKit
  class connectedShop : UIView{
  
      @IBOutlet weak var bannerViewHight: NSLayoutConstraint!
  
      @IBOutlet weak var bannerViewTop: NSLayoutConstraint!
      @IBOutlet weak var bannerViewLeft: NSLayoutConstraint!
      @IBOutlet weak var bannerViewRight: NSLayoutConstraint!
  
      @IBOutlet weak var banerDiscount: UIImageView!
      @IBOutlet weak var bannerImageShop: UIImageView!
      @IBOutlet weak var bannerTitle: UILabel!
      @IBOutlet weak var bannerDescription: UILabel!
      @IBOutlet weak var bannerButton: UIButton!
  
      @IBAction func bannerButtonAction(sender: UIButton) {
  
      }
  
      required init(coder aDecoder: NSCoder) {
          super.init(coder: aDecoder)!
      }
  }
  </code></pre>
  
  <p>And from the code I'm calling this shop like this:</p>
  
  <pre><code>let cShop = UINib(nibName: "connectedShop", bundle: nil).instantiateWithOwner(nil, options: nil)[0] as! connectedShop
  
  
  cShop.bannerTitle.text = "shopTitle"  //work
  
  
  shopContainer.addSubview(cShop)
  
  cShop.bannerViewLeft.constant = 0  //make my app crash
  cShop.bannerViewRight.constant = 0 // "
  cShop.bannerViewTop.constant = 0  //  "
  </code></pre>
  
  <p>When I set the <code>bannerTitle.text</code> property my app continues and debugging I see this outlet is initialized, but the constraints aren't and when the compiler are in the line that assign a constant, it always throw the same error:</p>
  
  <pre><code>fatal error: unexpectedly found nil while unwrapping an Optional value
  </code></pre>
  
  <p>debugging I've seen there is one outlet that is initialized:</p>
  
  <p><a href="https://i.stack.imgur.com/uYQkQ.png" rel="noreferrer"><img src="https://i.stack.imgur.com/uYQkQ.png" alt="enter image description here"></a></p>
  
  <p>Does anybody know why this can be happening?</p>
  
  <p>These are my conections:</p>
  
  <p><a href="https://i.stack.imgur.com/A5Jsk.png" rel="noreferrer"><img src="https://i.stack.imgur.com/A5Jsk.png" alt="enter image description here"></a></p>