Swift Callback Pattern

If you want an alternative to the protocol/delegate pattern, you can use callbacks. Here’s an example:

Example.swift

class Example {
  var onCompletion: ((result:String) -> Void)?
  func doSomething() {
    onCompletion(result:"here's the callback!")
  }
}

ViewController.swift

class ViewController: UIViewController {
  override viewDidLoad {
    Example.onCompletion = { result in
      print(result)
    }
    Example.doSomething()
  }
}

Once ViewController loads, “here’s the callback!” should show up in the console.

That’s it! You can use this pattern to get things done without having to abide by the strict “contract” logic of protocols.