let timer = Timer(0.5) {
  // do something after half a second passes...
}
timer.autorelease() // useful for fire-and-forget Timers
timer.repeat(2) // repeat twice
timer.repeat() // repeat until stopped
timer.stop() // stops the Timer immediately. alternatively, you could just set it to nil if the variable is an Optional
timer.fire() // completes the Timer immediately (only if not stopped)

class MyClass {
  var timer: Timer!
  func doSomething () {}
  init () {
    
    timer = Timer(1, doSomething) // this will cause a reference cycle!!!
    
    timer = Timer(1) { [unowned self] in self.doSomething() } // this prevents a reference cycle using a capture list.
    
    timer = Timer(1, doSomething()) // and this prevents a reference cycle using an autoclosure.
  }
}