UIKitDynamics - Gravity_Collision_Bounce

var dynamicAnimator   : UIDynamicAnimator!
var gravityBehavior   : UIGravityBehavior!
var collisionBehavior : UICollisionBehavior!
var bouncingBehavior  : UIDynamicItemBehavior!

dynamicAnimator = UIDynamicAnimator(referenceView: self.view) //1

gravityBehavior = UIGravityBehavior(items: [button]) //2
dynamicAnimator.addBehavior(gravityBehavior) //3

collisionBehavior = UICollisionBehavior(items: [button]) //4
collisionBehavior.translatesReferenceBoundsIntoBoundary = true //5
dynamicAnimator.addBehavior(collisionBehavior) //6

//Adding the bounce effect
bouncingBehavior = UIDynamicItemBehavior(items: [button]) //7
bouncingBehavior.elasticity = 0.75 //8
dynamicAnimator.addBehavior(bouncingBehavior) //9