amlcurran

extension Optional {
    
    func or(_ backup: Wrapped) -> Wrapped {
        if let wrapped = self {
            return wrapped
        }
        return backup
    }
    
}

amlcurran

// this is less descriptive and more difficult to read
if (user.getState() == LoginState.LOGGED_IN && articleList.getQueue().size() > 0) {
  uploadArticles();
}

// this is much easier to read and know what's happening
if (user.isLoggedIn() && articleList.hasQueuedArticles()) {
  uploadArticles();
}

amlcurran

func doSomething(optionalString: String?) {
  if let string = optionalString {
    let count = string.utf8.count // string is not optional and can be used normally
  }
}

func doSomething(optionalString: String?) {
  guard let string = optionalString else {
    // this closure is called if optionalString was nil
    return

amlcurran

let optionalString: String? = nil

let count = optionalString?.utf8.count // count is an optional Int

amlcurran

var string: String = "hello"
string = nil // fails to compile - trying to assign nil to a non-optional value

var optionalString: String? = "hello"
optionalString = nil // compiles fine, as we've declared this to be an optional string

amlcurran

class FirstViewController: UIViewController {
    
    private let items : [String] = [ /* some items */]
    private let tableView = UITableView()
    private var delegate : UITableViewDelegate!
    
    /* lots of other methods */
    
    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)

amlcurran

class FirstViewController: UIViewController {
    
    private let items : [String] = [ /* some items */]
    private let tableView = UITableView()
    
    /* lots of other methods */
    
    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        tableView.delegate = self

amlcurran

class FirstViewController: UIViewController, UITableViewDelegate {
    
    private let items : [String] = [ /* some items */]
    private let tableView = UITableView()
    
    /* lots of other methods */
    
    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        tableView.delegate = self

amlcurran

class FirstViewController: UIViewController, UITableViewDelegate {
    
    private let items : [String] = [ /* some items */]
    private let tableView = UITableView()
    
    /* lots of other methods */
    
    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        tableView.delegate = self

amlcurran

<link rel="import" href="../core-icon-button/core-icon-button.html">
<link rel="import" href="../core-toolbar/core-toolbar.html">
<link rel="import" href="../core-header-panel/core-header-panel.html">

<polymer-element name="my-element">

  <template>
    <style>    
      :host {
        position: absolute;