title: Fix width of element in UIStackView
body: <p>I create <code>UIStackView</code>s programmatically and add them to parent <code>UIStackView</code>, which is created in Storyboard. Child stack views are horizontal with 2 labels. I need to fix width of second <code>UILabel</code> and make the first <code>UILabel</code> fill the rest space.</p>
  
  <p>Now I have this:</p>
  
  <p><a href="https://i.stack.imgur.com/ckD9X.png" rel="noreferrer"><img src="https://i.stack.imgur.com/ckD9X.png" alt="Before"></a></p>
  
  <p>And I want this:</p>
  
  <p><a href="https://i.stack.imgur.com/sYgYO.png" rel="noreferrer"><img src="https://i.stack.imgur.com/sYgYO.png" alt="After"></a></p>
  
  <p>My code for generating children stack views:</p>
  
  <pre><code>@IBOutlet weak var parentStackView: UIStackView!
  
  func addStackViewsToParentStackView(params: [String: Float]) {
      for (name, value) in params {
          let parameterNameLabel = UILabel() // first label
          parameterNameLabel.text = name
          let parameterValueLabel = UILabel() // second label
          parameterValueLabel.text = value.description
          parameterValueLabel.frame.size.width = 80.0 // I've tried to fix width, but it does't help
  
          let childStackView = UIStackView(arrangedSubviews: [parameterNameLabel, parameterValueLabel])
          childStackView.axis = .Horizontal
          childStackView.distribution = .FillProportionally
          childStackView.alignment = .Fill
          childStackView.spacing = 5
          childStackView.translatesAutoresizingMaskIntoConstraints = true
          parentStackView.addArrangedSubview(childStackView)
      }
  }
  </code></pre>
  
  <p>Thanks for any help!</p>