init() and deinit() are called when objects are created and destroyed

Objects: initializing and deinitializing

Convenience inits that may return nil must be declared as failable inits

class Workout {

  let exerciser : Person

  let warmup : Exercising

  let primaryExercise : Exercising

  let coolDown : Exercising

  init (warmup : Exercising, primary : Exercising, cooldown : Exercising,

    exerciser : Person) {

    self.warmup = warmup

    self.primaryExercise = primary

    self.coolDown = cooldown

    self.exerciser = exerciser

    println("Stretching your muscles")

    println("Warming up cardio to raise heart rate")

    while exerciser.heartRate < (exerciser.heartRateResting +

      exerciser.heartRateTarget) / 2 {

      exerciser.heartRate += warmup.heartRateIncrement

      println (warmup.describe())

    }

  }

  func Exercise () {

    while exerciser.heartRate < exerciser.heartRateTarget {

      exerciser.heartRate += primaryExercise.heartRateIncrement

      println (primaryExercise.describe())

    }

    println("Target heart rate achieved")

  }

  deinit {

    println("Cooling down")

    assert(primaryExercise.heartRateIncrement > warmup.heartRateIncrement)

    while exerciser.heartRate > exerciser.heartRateTarget - 20 {

      exerciser.heartRate -= (primaryExercise.heartRateIncrement -

      warmup.heartRateIncrement)

      println (coolDown.describe())

    }

  }

}

var me = Person()

var myWorkout : Workout? = Workout(warmup: Walk(), primary: Jog(),

  cooldown: Walk(), exerciser: me)

myWorkout!.Exercise()

myWorkout = nil

println("myWorkout has ended")

println("My heart rate is now \(me.heartRate)")

https://gist.github.com/mthouser/4f8721f5fb89f5abb28f