Useful code snippets from Auto Layout by Tutorials book

Auto Layout by Tutorials.swift

// Chapter 1: Introducing Auto Layout
// Chapter 2: Construct Auto Layout with the Interface Builder

// 1
override func tableView(_ tableView: UITableView, accessoryButtonTappedForRowWith indexPath: IndexPath) {
  view.addSubview(contactPreviewView)
  contactPreviewView.translatesAutoresizingMaskIntoConstraints = false
  NSLayoutConstraint.activate([ // this line of code more performant than activating each constraint individually
    contactPreviewView.widthAnchor.constraint(equalToConstant: 150),
    contactPreviewView.heightAnchor.constraint(equalToConstant: 150),
    contactPreviewView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
    contactPreviewView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
  ])
  contactPreviewView.transform = .init(scaleX: 1.25, y: 1.25)
  contactPreviewView.alpha = 0
  UIView.animate(withDuration: 0.3) {
    self.contactPreviewView.alpha = 1
    self.contactPreviewView.transform = .identity
  }
}

// 2
@objc
private func hideContactPreview() {
  UIView.animate(withDuration: 0.3, animations: {
    self.contactPreviewView.transform = .init(scaleX: 1.25, y: 1.25)
    self.contactPreviewView.alpha = 0
  }, completion: { _ in self.contactPreviewView.removeFromSuperview() })
}

// 3
// Setting up class to "File's Owner"

// 4
private func loadView() {
  let bundle = Bundle(for: ContactPreviewView.self)
  let nib = UINib(nibName: "ContactPreviewView", bundle: bundle)
  let view = nib.instantiate(withOwner: self).first as! UIView
  view.frame = bounds
  addSubview(view)
}

// Chapter 4: Construct Auto Layout with Code
NSLayoutConstraint.activate([
  stackView.leadingAnchor.constraint(greaterThanOrEqualTo: leadingAnchor, constant: 20), // 1.0 giving range of constraint 
  stackView.leadingAnchor.constraint(lessThanOrEqualTo: leadingAnchor, constant: 500), // 1.1 giving range of constraint 
  
  profileImageView.widthAnchor.constraint(equalToConstant: 120), // 2.0 configuring aspect ratio 1:1
  profileImageView.widthAnchor.constraint(equalTo: profileImageView.heightAnchor), // 2.1 configuring aspect ratio 1:1
  
  leftSpacerView.widthAnchor.constraint(equalTo: rightSpacerView.widthAnchor) // 3.0 giving equal width for two views
])

// Chapter 5: Scroll View

// Scroll view has two layout guides
// 1. scrollView.contentLayoutGuide
// 2. scrollView.frameLayoutGuide

private func setupMainStackView() {
  mainStackView.axis = .vertical
  mainStackView.distribution = .equalSpacing
  mainStackView.translatesAutoresizingMaskIntoConstraints = false
  
  scrollView.addSubview(mainStackView)
  
  let contentLayoutGuide = scrollView.contentLayoutGuide
  
  NSLayoutConstraint.activate([
    mainStackView.widthAnchor.constraint(equalTo: view.widthAnchor),
    mainStackView.leadingAnchor.constraint(equalTo: contentLayoutGuide.leadingAnchor),
    mainStackView.trailingAnchor.constraint(equalTo: contentLayoutGuide.trailingAnchor),
    mainStackView.topAnchor.constraint(equalTo: contentLayoutGuide.topAnchor),
    mainStackView.bottomAnchor.constraint(equalTo: contentLayoutGuide.bottomAnchor)
  ])
}

let insets = UIEdgeInsets(top: 0, left: 10, bottom: 0, right: 20)
let image = UIImage.init(named: greenBubbleImageName)?.imageFlippedForRightToLeftLayoutDirection()

bubbleImageView.image = image?.resizableImage(withCapInsets: insets, resizingMode: .stretch)

// Chapter 6: Self-Sizing Views
override func layoutSubviews() {
  super.layoutSubviews()
  let height = collectionView.frame.height - verticalInset * 2
  let width = height
  let itemSize = CGSize(width: width, height: height)
  flowLayout.itemSize = itemSize
}