title: What is the difference between Top and TopMargin in NSLayoutAttribute?
body: <p>I am trying to create a constraint via code:</p>
  
  <pre><code>constraintImageCharacterTop = NSLayoutConstraint (item: image,
          attribute: NSLayoutAttribute.Top,
          relatedBy: NSLayoutRelation.Equal,
          toItem: self.view,
          attribute: NSLayoutAttribute.Top,
          multiplier: 1,
          constant: viewTop)
      self.view.addConstraint(constraintImageCharacterTop)
  </code></pre>
  
  <p>However, I am not sure which is the right <code>NSLayoutAttribute</code> for this constraint. <code>image</code> should have a top space to the main Superview <code>self.view</code>. </p>
  
  <p>This is how I think it works, but I am not sure if I am correct:</p>
  
  <p><img src="https://i.imgur.com/2ws4LEK.png" alt="Imgur"></p>
  
  <p>Should I use <code>NSLayoutAttribute.Top</code> or <code>NSLayoutAttribute.TopMargin</code> for image A? </p>