Once in Swift

Contents

1. 1. dispatch_once
2. 2. Once

There are times we want to run an action just once. It would be nice if we can encapsulate this

dispatch_once

dispatch_once is meant to be used for action that runs once and only once

Once

We can have

class Once {

  var already: Bool = false

  func run(@noescape block: () -> Void) {
    guard !already else { return }

    block()
    already = true
  }
}

Then we can use it like

class ViewController: UIViewController {
  let once = Once()

  override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)

    once.run {
      cameraMan.setup()
    }
  }
}