ElasticViewController_statemachine_delegate.swift

func elasticMotionStateMachine(stateMachine: ElasticMotionStateMachine, didChangeState state: ElasticMotionState, deltaPoint: CGPoint) {
  switch state {
  case .MayOpen:
      let newOriginX = self.view.frame.origin.x + deltaPoint.x
      if newOriginX >= 0 && newOriginX < CGFloat(threshold) {
          self.view.center = CGPointMake(self.view.center.x + deltaPoint.x, self.view.center.y)
      }
  // other state
}