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@discardableResult
func example() -> String {
  let description = "This is an example"
  print(description)
  return description
}

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func example() -> String {
  let description = "This is an example"
  print(description)
  return description
}

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var value = example()
value.append(" with discardable")
print(value)

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let a = UIView()
let b = UIView()

a.topAnchor.constraint(equalTo: b.topAnchor)

let aBottom = a.bottomAnchor.constraint(equalTo: b.bottomAnchor)
aBottom.priority = .defaultHigh

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let containerView = UIView()
view.addSubview(containerView)

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let layoutGuide = UILayoutGuide()
view.addLayoutGuide(layoutGuide)

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[photoImageView, introLabel].forEach { self.view.addSubview($0) }

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NSLayoutConstraint.activate(
  [
    layoutGuide.centerYAnchor.constraint(equalTo: view.centerYAnchor),
    layoutGuide.leadingAnchor.constraint(equalTo: view.leadingAnchor),
    layoutGuide.trailingAnchor.constraint(equalTo: view.trailingAnchor),
                
    photoImageView.topAnchor.constraint(equalTo: layoutGuide.topAnchor),     
    photoImageView.centerXAnchor.constraint(equalTo: layoutGuide.centerXAnchor),
    photoImageView.widthAnchor.constraint(equalTo: photoImageView.heightAnchor),
    photoImageView.heightAnchor.constraint(equalToConstant: 250),

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// Subviews
let logoImageView = UIImageView()
let welcomeLabel = UILabel()
let dismissButton = UIButton()

// Add Subviews & Set view's translatesAutoresizingMaskIntoConstraints to false
[logoImageView, welcomeLabel, dismissButton].forEach {
    self.addSubview($0)
    $0.translatesAutoresizingMaskIntoConstraints = false 
}

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extension UIView {

  func addSubviewsUsingAutoLayout(_ views: UIView ...) {

    views.forEach {
      self.addSubview($0)
      $0.translatesAutoresizingMaskIntoConstraints = false
    }
  }
}