如何从scrollView视图中删除某些视图Array swift

Question

我有一个分页的scrollView，我想删除未显示（或动画）的视图。我不能解决它。我想从显示的视图中清除-1和+1视图之外的视图，以减少内存。

func addViewController(vc:UIViewController)->Void{


controllers.append(vc)

// Setup the viewController view

vc.view.setTranslatesAutoresizingMaskIntoConstraints(false)
scrollview.addSubview(vc.view)

// Constraints

let metricDict = ["w":vc.view.bounds.size.width,"h":vc.view.bounds.size.height]

// - Generic cnst

vc.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:[view(h)]", options:nil, metrics: metricDict, views: ["view":vc.view]))
vc.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:[view(w)]", options:nil, metrics: metricDict, views: ["view":vc.view]))
scrollview.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-0-[view]|", options:nil, metrics: nil, views: ["view":vc.view,]))

// cnst for position: 1st element

if controllers.count == 1{
  scrollview.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-0-[view]", options:nil, metrics: nil, views: ["view":vc.view,]))





  // purge controllers.count > 2 




  // cnst for position: other elements

}else{

  let previousVC = controllers[controllers.count-2]
  let previousView = previousVC.view;



  // purge controllers.count before previousView



  scrollview.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:[previousView]-0-[view]", options:nil, metrics: nil, views: ["previousView":previousView,"view":vc.view]))

  if let cst = lastViewConstraint{
    scrollview.removeConstraints(cst as [AnyObject])
  }
  lastViewConstraint = NSLayoutConstraint.constraintsWithVisualFormat("H:[view]-0-|", options:nil, metrics: nil, views: ["view":vc.view])
  scrollview.addConstraints(lastViewConstraint! as [AnyObject])



}