NSLayoutConstraints breaking but seem fine
<p>I'm trying to pin an image view to the top, left, and right of a superview, and give it a height with <code>NSLayoutConstraint</code> like so:</p>

<pre><code>backgroundView.addSubview(imageView)
backgroundView.addConstraint(NSLayoutConstraint(item: imageView, attribute: .Top, relatedBy: .Equal, toItem: backgroundView, attribute: .Top, multiplier: 1.0, constant: 0.0))
backgroundView.addConstraint(NSLayoutConstraint(item: imageView, attribute: .Left, relatedBy: .Equal, toItem: backgroundView, attribute: .Left, multiplier: 1.0, constant: 0.0))
backgroundView.addConstraint(NSLayoutConstraint(item: imageView, attribute: .Right, relatedBy: .Equal, toItem: backgroundView, attribute: .Right, multiplier: 1.0, constant: 0.0))
backgroundView.addConstraint(NSLayoutConstraint(item: imageView, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1.0, constant: view.bounds.width))
</code></pre>

<p>But the image doesn't show up and the debugger is logging that my constraints are broken. I don't see what constraint could be causing the problem.</p>